I don't think transom savers are designed to take the weight off the transom - rather, they are designed to keep the motor from bouncing up and down when you go down the road, thus "saving" the transom from damage. If I am wrong.... then think of this - when your boat is in the water, what is saving the transom then??? When on the trailer, if it is locked in place with the Lock N' Stow (same basic principal as the old Johnson/Evinrude style flip downs... just one step further - it doesn't allow side to side movement either), then the motor doesn't bounce up and down on the transom. With the old type that goes to the trailer frame, it keeps the motor fairly safe by locking it in place, but it is more prone to allowing bouncing AND the shock from the trailer if it hits a large pothole, etc.... It also doesn't exactly do a good job of keeping the motor from turning side to side - especially with a 200hp engine and above. I had one of the regular types on my 225 Opti when I first got the boat, and I had to put the little plastic steering ram locks on my hydraulic steering because the engine would move side to side. Think of it this way - that engine weighs hundreds of pounds. Do you really think that little piece of 1" aluminum tube is supporting ALL the weight of that engine??? Nope. Your power trim ram is. The Lock N' Stow is a lot more stable IMO.
All the best,
Glenn