Some boat trailers have power tongue extensions. Possibly a manual version of same exists, I don't
know for certain.
I would not take the chance that you might dunk your generator, either by submersion or wake.
If you're not sure, ask about it at the point of purchase. I suspect they will tell you not to submerge
it at all for any reason. Beyond that, it's up to you. There's going to be a certain amount of road water
that gets to them while driving in rain, and so on, but it's the dunk that will make it clunk.
Think "voiding my warranty".
As for drive through car washes, it's the height and length that may limit it. Some manual
car wash bay doorways may also be too short for the raised roof and any add-ons topside.
Fast food and other drive thrus may also now be out of bounds for you.
Don't trust the - 9' 6" tall clearance - signs at the entrances to the drive thru lanes, as we've seen (and measured) one or two that weren't accurate.
Rule of thumb, if there's any doubt, use a "spotter" when attempting any of these maneuvers. It IS
worth the hassle.