Disclose it. I've always shared as much info with a private seller as I can, most were new RV owners and didn't know what to ask. I've never had a lemon so no issues.
I traded in a Toy Hauler and kept waiting them to ask questions, all they asked was the condition and my honest reply was it's in good condition. I did have a brush with a tree branch, no leaks and I did the repair with EternaBond tape. They called later, after all the papers were signed and said I had failed to disclose the damage. I told them you never asked about any damage, I think they realized they handn't I told them all about it, and that I'd even bought the EternaBond tape from their parts department!