Coming from lots of experience with Yakima, I say do NOT buy their Q-tower based cross bars over the cab. On three Tacomas I've seen them put some dents in the side of the roof (no, I did not tighten mine down too much). They do however work really good on other vehicles.
I switched to a camper shell with a steel ladder rack and haven't looked back ever since. Expanded metal on top allows you to climb around. The four rising legs allow you to tie add'l boats on the side. Like Bob said, 1000s of lbs.
History will be kind to me, for I intend to write it.