This is what I use under my transom lower the tongue all the way down insert and then pick up the bow through the trailer winch eye with a chain fall. It’s what I use for bottom paint and trailer work I hope this helps
I’ve used your #2 option with additional 3m below waterline around the pad to seal out water. Solid going on four years my tracker Grizzly is powder coated so I was confident in its adhesion they do send a scuffing pad and alcohol wipes also I only used a normal transducer not the longer side...