Forgot to mention as I found on my trip I just got back from. Pad was 45' but I couldn't fit.
Why?
Because the site wasn't level enough.
With a shorter trailer, it could be leveled because you have the option of moving it to a spot that will allow it to be level. In my case, it was side to side leveling.
For the case of a co-camper that was fighting to fit his camper into the spot as I was, his campsite sloped down to much and he couldn't get his hitch down enough to be level.
We were both upset as we reserved for 5 days each, and campground was pretty booked up. We got extremely lucky and I was able to get the site next to mine as someone must had cancelled and he was able to get a site in a different part of the campground. There are about 350 sites but it's a popular campsite being it's a peninsula surrounded by the lake.
So it's not always about length of the campsite but how much harder a long trailer is to level as well.