My fiver is 37ft. with 3 slides. We have camped in state parks in Fla. and Ga. over the last couple of years and have not had any problems finding spots. The same sites would have worked for a 40 ft. unit also. A number of these parks have pull-thrus others you may have to unload your toys before you back in. Also a couple of times the site was plenty large but it took a little work to back in due to the narrow roads etc. But they were all do-able. If you want a 40ft. rig go for it. My next rig will be bigger also.