So you are sumping? Are you planning to drill the 29 or run a hang on overflow, drilling is better and you could fabricate an overflow weir cheap if you don't mind it being noisy.
I'm going to suggest a larger sump size. I tried a 10 gallon on my 29 and with my skimmer and return pump in there, when I shut my tank off there wasn't a lot of space for draining water from the display during power outages. I currently use a 20 high, same footprint as a 15 gallon. I got three sections in there, used a precut sump kit from eBay. First section houses chaeto, extra rock, heater. Second houses my oversized reef octo classic 110-int skimmer. Third houses a supreme mag drive return pump.