I've never been a big fan of the smaller mounting plates. I prefer the bigger ones myself. Unfortunately, Cabela's stopped selling the larger ones. We actually purchase oversized cutting boards and cut them down.
I simply do not trust the adhesive.
The picture below shows the boards that we use and the size of them. If there are any rivets or anything where the board goes, we recess the board before installation. This photo shows the side image transducer on the outside. I was tired that night and placed it to the inside the next day when I found the error of my ways. All screw holes are above the water line (total of 5 stainless screws). A small amount of marine grade silicone is placed on each screw. In the event you are going over existing holes, recess the board really well, insert a screw with silicone to plug the hole, and then fill the recess with silicone before installing the board. No need to put silicone around the board.
My fish finder reads bottom at 45mph. IF adjusted correctly, you shouldn't lose bottom.
I have OCD "Obsessive Crappie Disorder"