Large-Format Print Enlargement using a Shen Hao 5x4" View-Camera
Over the past year, I have taken up using a Shen Hao large-format view-camera and started developing my own black and white films myself, using the bathroom as a darkroom. I was looking for a cheap and convenient way to make small (2*, up to 10x8") enlargement prints, particularly from 5x4" black and white negatives, but without the expense of buying a proper large-format enlarger (to say nothing of the space such a thing would occupy). Along the way I spent some time looking for a "Graflarger", a replacement film-back for cameras with a Graflok-compatible back; however, since these are impossible to find even second-hand, and it seems pretty obvious that if the light can come in through the lens one way, it can be projected back out the way it came (in the style of a "magic lantern"), I thought I would attempt to build my own.
In practice, the equipment required is pleasantly minimal. Jessops sell an ideal small lightbox - very thin and light-weight, with a 5x4" white panel on the front. Of course, this does not fit directly into the Graflok back, so I asked a local glazier to cut down a piece of glass to exactly 17x17cm, to which I affixed the lightbox with tape. The negative simply fits sandwiched between the glass and lightbox; the glass then fits into the graflok back neatly between the retaining sliders. A small amount of blu-tak or equivalent is required to stop it wobbling back and forth.
As might be deduced, I do not intend this to take the place of serious darkroom with an enlarger, timer and easel, but it does demonstrate that favourable results may be achieved at home without such. Take all numbers quoted with a pinch of salt: results will vary depending on your choice of paper (I use Ilford and Foma RC), developer (Maco Ecoprint), temperature (20C give or take 1C), focal length and cleanliness of lens (Rodenstock 210mm), and of course on the contrast of the negative you're projecting!
Equipment
The dry parts: Shen Hao 5x4" camera, Rodenstock 210mm lens, Jessops lightbox mounted on glass with film negative loaded: 
Preparing the wet parts: two trays (for developer and fixer/washing), a bottle of fixer, some Maco Ecoprint developer concentrate, two measuring cylinders, and a funnel (for reusing and replenishing developer and fixer). You'll see here I've got the shower running with cold water, to help remove dust from the atmosphere when dealing with films and hanging prints out to dry.
Thus loaded, the Shen Hao is mounted on a sturdy tripod (in this case, my Slik D3) and placed pointing at a wall on which I've blu-takked a piece of photographic printing paper, back-side facing forwards. (It helps to use a piece of paper that's already been exposed and developed for testing - it can later be reused for dodging and burning during exposure.) 
A closeup of the Shen Hao with lightbox mounted on glass in the graflok back:
Note: the easiest way to align everything is to start by projecting the image through the camera onto the opposite wall. Then affix the photographic paper in about the right place, and make fine adjustments using the camera's movements - they work the same as when making the original photograph, so shifting the lens up and down is particularly useful. If you use a dark wall, the contrast between projected image as reflected off the paper and from the wall will make it easy to tell where the image will be cropped.
You need to focus the camera quite accurately, so make sure the paper is reasonably taught, and prepare to rack out the bellows a bit. In practice, you'll be stopping the lens down to at least f/16 and maybe even more, which gives both lots of depth of focus (ie leeway for the paper to be warped or misplaced) and lots of time in which to dodge & burn the image if required.
Setting up to print: this shows the projection working, with the image formed on the test-paper.
When you're happy that the image and paper are correctly placed, close the shutter, turn off the lights, switch to a new sheet of paper, and stand to one side of the light-path. It is vital that you only move minimally on the floor, otherwise the motion will jar the camera giving a very blurred print.
Stop-down the shutter to at least f/16, maybe even as far as f/32. Open the shutter and start timing the exposure. With my light-box, for a 2* enlargement (ie up to a 10x8" print) I start from a (very convenient) 1 minute at f/16 rising to 3min30s at f/32, subject to dodging or burning-in. Be careful not to shake the tripod and camera whilst moving your hands or other obstacles in the light-beam.
When done, transfer the paper to a tray and develop it. In my case, a 1+15 dilution of Maco Ecoprint suffices for development by inspection over the course of about 1min15s.
After development, I transfer the print to the second tray, in which I give it a quick rinse under the shower to remove the developer, prior to applying fixer.
First print being fixed:
After half a minute in fixer solution, you can turn the lights back on and inspect how it really looks.
After a couple of minutes the fixer can be poured back into a bottle for replenishing every couple of prints; the print must then be thoroughly washed for a further couple of minutes to remove all traces of fixer. If you use a tray for this and fill/empty it repeatedly, you can add a wetting agent to break the surface tension, to save getting drying-marks on the print.
When you're finished, hang the print up to dry:
If you're not satisfied with the first masterpiece, go back and repeat the process!
Image sharpness depends on four factors: first, the camera must be focussed on the paper fairly accurately. The distance from camera to paper depends on the focal length of the lens and desired enlargement factor; if you focus with the lens open at its widest aperture, that will be the most accurate. Second, stopping-down to f/16 or less will buy you depth of focus and longer exposure times (double it for each stop). As an aside, the lens probably has an optimum sharpness somewhere in the middle of its aperture range. Third, the camera must be rigidly mounted on the tripod and not disturbed during the exposure. I recommend using a room with thin or no carpet, a cable-release, and standing very still but within reach for dodging and burning - move only your torso not feet during exposure. It helps to have a shutter (such as Copal 0) with Timer (T) mode as well as Bulb (B). Fourth, the nature of the lightsource in the lightbox is significant; proper conventional enlargers have the options of using condenser or diffuser heads. However, there is little one can do about this easily.
The final print shows lots of detail. The following picture was enlarged onto Foma RC paper, developed in Maco Ecoprint, scanned on an Epson V700 flatbed scanner, full platen at 900dpi giving an image approximately 10,000px wide prior to rescaling:
(Sun breaking through mist, early morning sunrise, Glen Affric.)
Update: I have now successfully used this technique to print an enlargement off square 6x6-format 120 roll-film. Using the Hasselblad 500CM and Ilford Delta 3200 film rated EI1600 (ie pulled a stop), I have a very satisfactory enlargement from about the width of the frame up to 10" wide with little grain present. Because the lens is further away from paper to give a greater enlargement factor, the exposure numbers change; I found about 2.5 to 3 minutes at f/16 was a good starting point.