Does anyone have any opinions on a Turbo TXP OT-4? They are supposed to be good for very high mounted engines on lightweight go fast boats, have very good grip and very good control. They are over and thru hub. But, for some reason, they make both a vented and unvented version. I found them brand new for $547+ shipping, with the hub. $20 more for the vented version. Has anyone used them? Got an opinion?