In short, I really don't reccomend it.
Mechanically it will all fit in a desktop. However phase5 made it perfectly clear that neither the BPPC or BVision should be used in anything other than a tower case.
As NicoPPC demonstrates, you can get away with it, but you are literally pushing the design into areas the manufacturer did not think sensible.
I have a BVision and I can tell you that you can burn yourself on the P2. It dissipates quite some heat at 83MHz and really should be fitted with a heatsink (info taken from TVP4020GFN hardware manual) in a normal PC environment (which has better aiflow than a A1200D), active cooling is reccomended at 90MHz.
Add to this the heat generated by the PPC, voltage regulators, 68K, memory and hard disk (if 3.5 inch) and you are way above what the A1200 case was designed to cope with.
