Hi geekengineer!
Thanks for the link to your build - I didn't realize you had a 29 in the works, thought just the 10. How exciting! You seem to be almost finished from the looks of it.
Any progress with the auto-shutoff circuit for your overflow system? I would probably make that my main priority before stocking the tank just to make sure you have everything together and working properly. Too easy to get sidetracked with other idea's and then you put if off too long and bam, flood.
Concerning your idea on a back wall - I'm including a link for a guy who did one on his 40 breeder out of foam. Start on page 3. It works for him as he did it on a tank with depth since he loses about an inch or so of space, but for your 29 its already narrow so you would lose precious landscaping space front to back.
http://www.reefcentral.com/forums/showthread.php?t=2486801&page=3
I would hold off on stocking the 29 until you have your overflow failsafe in place (and tested several times) and an ATO figured out. Doesn't mean you can't fill it with saltwater and have it running to tweak things, but nothing alive that could clog your overflow before you have your failsafe setup.
I got some bad news concerning my timer ATO I was using so am presently inbetween methods on that. Better to have something in place before rather than having to rush something together after the tank is up and running.
BTW, the hanging pendant looks really good. I saw some guys that use a DIY screen cover for the tank that you may want to check out if you don't want to go with the eggcrate.