We've stayed there with a 37' 5th wheel. We found the sites to be very level, but you're right - there was a fairly sizable slope to our last site that required a little more perseverance to get into. There are a limited number of large rig sites. Most seem more suited to those under 30'

We stayed there twice with a 43 foot 5th wheel, we stayed in the pull through area and everything was pretty level. The other sites for rigs my size would be tough.