Cvanhook,
I can't help you with the RTT and having a Suburban or a Tahoe makes an RTT kinda redundant and a useless and unnecessary weight on the roof, but that's just my two cents.
I can help you out with a bomber root rack that will support the RTT and anything else you want to put up there.
https://www.expeditionportal.com/fo...ow-lift-with-37-s.166120/page-21#post-2428914
This is the roof rack I built nearly five years ago and it has been nothing but solid even on a 10,000 mile trip to Alaska and back with 800-1,000lbs on the roof so it would support a RTT with no problems whats so ever.
Good luck!