How about a river?
Why not hook up the muffs and see how it runs in the driveway?
When I bought my boat years ago I did the same as you.
We took it for a test ride. But I had to prove I had the money to buy the boat.
Seems fair to me.
A member from here brought a friend to look at a truck.
He left a deposit before taking it out.
Something to think about doing if and when the seller requests it.
I would do the same.
I recently bought a truck. Drove 9 hours one way. The guy knew I was serious when I showed him the money.
So test driving it wasnt an issue.
Try a river for your test and stay away from water falls