I can answer parts of your question. A bike with a sloping top tube should still fit in the rack, unless it's an extreme slope (can't see your bike, but can't really picture what bike wouldn't be okay). Full-sus DOES require a bike beam though.

Sorry, I've never tried locks for my Bones rack - without locks it would be very easy to steal, everything loosens quickly.

Good luck!

P.S. Just received a Yakima hitch rack for the new SUV, and it is sweet - locks and all