Reminds me a bit of myself years ago. None of my computers were in a case. Too much trouble to make changes that way. Simply hang the motherboard on a nail or two in a piece to plywood leaning up against the wall. Bingo, computer! It was also much easier to keep them cool that way.
should have known earlier how to cool. must always multiple options in mind. sitting on a two-stage mobile table was not the best idea. near the windwo which must be openend. a lot of troubles when touching the MOBO all the time. videocard now stabilized with metallic string. yes its protected. killed one MOBO when agp-slot was wobbling all the time when videocard was touched. an the special pcu-cooling from below, no from the side. new coming cpu sempron 3000+ has best compromise.
new MOBO will have working PCI-slots.
Computer near an open window?
I do know what you mean about properly supporting stuff. Been there, done that.