We stayed in a couple of provincial CG's last summer in Jasper Natl Park. At one particular park we were told that their largest sites only accommodate up to 36'. Since I have experienced that in the past, I asked if I could ride my bicycle around the CG and see if there was something I could fit our 40 footer into. They said sure, as long as I realized that the motorhome would have to be completely off the road and the tires had to be on the paved pad.
I rode around and found two sites that I could easily fit our 40' into because the rear end was able to overhang the back of the site and still keep front and rear tires on the 36' paved pad. In fact, there was room enough to park a car in front of the RV, although I wasn't towing anything at the time.
My point is, even though CG's have a certain length of pad, it is worth visually checking to see if a larger rig can fit into the sites and not be blocking the access road or parked on surrounding vegetation(off the paved pad). No harm in asking if you can look at their sites.