[Ryank]

I had a 20 and ran several different engines on it. I was slightly worried about a 30 yr old transom myself even though it had little flex. I had an aluminum plate cut out to the shape of the transom and a smaller plate on the inside and it had raised the height by about 5-6 inches kind of as a splash shield. I had to use a jack plate to do this and use a 20 inch shaft engine. When I purchased a new engine I purchased a 25" shaft and then had to adjust / raise the jack plate which helped to get the cav plate about 1 1/2 inches above the bottom and proper trim, and it also raised the power head up and out of the water quite a bit helping to protect it from salt water etc. Boat handled great for several years and I never ever worried about the transom again. If yuo are worried about the transom a great deal I would not put a large bracket on it without having it inspected by a pro first. A jack plate is not quite as much stress.
Just my .02 cents. Hope this helps