Bike porn

the very latest SS-Evo frames that are currently being raced there is a fairly strange looking cutout/straight-through section above the BB to duct the air, so it's clear that it is something that they are thinking about.

I'm pretty sure that gap is not related to aerodynamic development, and I'd hazard a guess that it's actually worse to have a hole there than it would be to plate it over, albeit by only a tiny bit since the air there is all but stalled and completed fucked* by the cranks. The speculation is that the split seat tube is to make it more laterally stiff and vertically compliant™

*http://en.wiktionary.org/wiki/windfucker