Based on your needs for a TT I'm not sure you'll find one your F150 can pull safely.
We've been involved in off road racing for many years. Our first TT was a 23 FT Nomad. It sat on top of the axles so there was plenty of clearance. It was considered a mid-level quality RV. We used it to get in and out of the main pit areas at the races... usually a hard pack dirt road with bumps, rocks and some sand. No problems the TT held up well. I pulled it with a Chevy 2500 4X4.
You will be surprised at how well most TT & RVs will hold up to offroading as long as you are careful.