I have been researching this for mounting my new Helix 5 SI transducer on my 1648 flat bottom. Going with no screws and 3M 5200 is a fine method, however, most of the advice I have read said it works best if the boat transom mounting location is coarsely sanded then wiped with acetone. It's also recommended to even "mill" (prob not the correct term) out some grooves/pockets in the cutting board for better adhesion.