@Marina: As far as I know, the rules prevent suits that cause buoyancy (like a wetsuit would), so any suit proven to enhance buoyancy wouldn’t be allowed. At the same time, everyone has access to the suits, so although it may impact records, everyone has the same chance at breaking them.
And yes, the tighter the suit, the faster you go. That’s why they’re so darn to put on. I have on many occasions needed help putting on a FastSkin.