I don't know what loop you are in but we have no problems with a 34' fifth wheel. The roads in the park are hilly but fine. The roads in the camping area are nice too. The loops are one way and you should not have an issue. Some have a some lower branches hanging but hopefully not an issue. The park is BIG and lovely. There are 3 entrances into the park; north, south and west. Lots of beautiful places to take pictures and a lot of history at the south end - be sure to see Mary Jemisom area.
Parents who still don't know anything
Twin college graduates who know everything
One lazy Westie
2000 F350 DRW 7.3 PSD crew cab
2007 Jayco Eagle 291 RLTS
2003 Coleman Sedona towed by 99 4Runner for the "graduates"
I had no problem getting my signature TT into a spot at Letchworth last year, but my camping partner has a Jayco that's a bit longer. Because of the angle, we had to pull the 4x4 site marking post out of the ground, so that he could make the cut into the site. It was loose, so I think that we weren't the first one's to have to do this.