I did a conversion years back now, into a 'full tower'.
I bought a 90-degree PCMCIA adapter, removed the rear of the tower, had a new one plasma-cut with a long slot so you could see all the 1200s connectors vertically - made my own PSU-1200 lead (plans on Aminet) - made my own RGB-VGA adapter (again, thanks Aminet), rotated the tower's PSU by 90-degrees (so it was flush against the top rather than positioned vertically).
Everything worked fine first time. I had to add some insulation behind my Blizzard card but other than that (which was the bottom from a plastic lunch box) I just screwed it on using brackets that held the corners of the motherboard.
Also fitted an EZ-Key interface, added an A4000 keyboard, Squirel SCSI with a reno CDROM (this was later dropped and I put a real CDROM in the tower with an unbuffered IDE Interface) etc etc.
It was nice. I even relocated the original 1200s lights to one of the faceplates of the tower with a large Amiga sticker over the front so they shone through.
Shame I sold it all a couple of years ago due to lack of space!
Matt