Thanks jesto, I'm following yours as well, and of course you're in good hands. Feel free to steal away!
A few things to keep in mind, in case any of it helps:
- The 3" lights I used (sent a link to Jeff) are halogens, so they run hot. The base of the cans is permitted to lie directly on drywall or wood ceiling (bottom of the soffit in my case) though. Since my soffit is fabric covered (although fire retardant), I may add thin masonite rings under them to keep them off the fabric, not sure yet. I tested yesterday, leaving them all full on for an hour, and felt the trim rings, they do warm up, but not nearly as hot as the fixture itself.
- They are plenty bright; actually, if I had planned on doing the soffit with lights from the outset (it was a late addition, not in the original plan), I could easily have skipped the ceiling cans. My space is 23x17 (21x17 taking away the false wall), and there are a total of 14 3" cans in the soffits - 5 on each side, and 4 in the back. Brighter than running the 6 4" ceiling cans.
- If you're planning columns, work out the can location with them in mind; I had to balance between spacing them neatly between columns, or having them evenly distributed along the soffit, and I close the latter, to keep the lighting fairly even.