I've always had a 38ft RV and I don't feel limited at all. I camped in National parks and when asked how long I say 35ft( for those with that limit), no one ever measured and I've never not fit. Those 3 feet don't make a difference.
I actually prefer not to camp IN the national parks. The National parks often have horrible amenities, i've had my share of black outs, water outages, etc.
But in Yosemite for example there are 4 campgrounds that have a 40 foot limit, so if I was 42 feet I'd just tell them I was 40ft.
In Sequoia National park they have sites up to 62 feet long, so I think you should be more acquainted with your own state. You don't have to live there to read the rules.
