Check out Trax Tech tracks. I run two Big Jon Brutes that I slide into 16" tracks mounted on the transom. I also have gimbal mount tracks that hold my rod holders. Awesome quality products.
I agree with tbromund. I have two beefy bags that are going into their fourth season. Give Capt. Frank a call and he'll direct you to the proper size bag. I can't say enough about the quality of his product...........
Transom mounting plates are the way to go.You only need to drill two holes to attach it.This way if you make a mistake you are not putting extra holes in the transom.$10.00 bucks at Gander or your freindly marina...........