I would be interested in building a racing SUP, but I have to build the paddle board first! I have never paddled one of the racing boards but I have seen plenty of videos on youtube and those things really move.
I almost put a drop in the top skeg on the jem board but wound up going with 2 long runners at the rear. It would be neat to have something that could push up if you got in shallow water and then spring back down. One thing about a stand up paddle board, if you hit a rock or something, and your not ready for it. You meet the water! Trust me, I know
I might do a little experimenting with skegs soon.
I think I'll add a slightly rounded deck to ensure water sheds off quickly. The only drawback to doing that is it takes a little more work to install a twist-out hatch, if a builder wanted to do that for car keys or a water bottle.
For racing class, internal deck storage isn't a high priority. But it's nice to have the option.