A Venture corvette can easily do a barrel roll in standard atmosphere, it is simply a matter of timing and altitude.Also, if you were wondering what's up with the ordering 3D prints of Klavs' design, here's the latest on Terran Fleet Supply:
TCFT Report titled 'Unconventional manuvers in conventional craft' by Todd Marshall (rejected for publication)
Still working on it. Think I'll stick with Shapeways for now and keep the shop open there. They won't let you order any of the ships with problems, so the ones that are still available for purchase should print okay.
I'll eventually be working on some lower detailed models for the problem ships that should print with fewer problems.