Darby/Sulu, Montana Info??

Heading to Jellystone and Grand T's mid May. Going down US93 to MT43, and planning a 3-5 day dry camp in the area SW of Darby along MT473. Any info from "experienced" Montana campers aboot Rombo NF CG and Sam Billings Memorial NF CG, or any other "great" boonie sites.

We are 34 ft trailer and Excursion, 53 ft overall. Both sites state 30 ft trailer max, although Rombo shows quite a few large pads online. If not a good idea, we will use Indian Trees NF CG, know we can go in there!!

Just looking for local knowledge, and any unexpected negatives before finalizing plans!!

Thanks ahead of time to y'all!!