The key is a triangle. If you look at the the bracing for tresle bridges, the support structure for a domed stadium, or numerous other things you always find triangles. You need to form a triangle with the 3 sides being 1) the transom, 2) the motor, and 3) the transom saver.

Next you need to secure things. I've used a swivel-eze transom saver on my 12 ft aluminum boat with a 15hp outboard with manual trim for over 10 years with no problem. The key things were to 1) adjust the length of the transom saver so the motor is at an angle of about 45 degrees to the transom, and 2) secure *both* ends of the transom saver.

For my boat I used rubber straps with hooks on the ends. The motor end is easy, it just goes around the motor just above the port and hooks into holes on the transom saver. The trailer end is a bit trickier. The transom saver has a semi-circular end to fit on a roller, so I added a roller that is not in contact with the boat specifically for this purpose. I then hook one end of the strap to the trailer frame, pull it tight, wrap it a few times around the transom saver and then hook the other end to the trailer frame on the opposite side of the transom saver. This keeps the transome saver pegged to the trailer and keeps the motor from bouncing.

On my new boat the back end of the trailer is so far under the boat, the standard straight transom saver won't work, but cabelas has a model that is extra long and has a bend in the middle. It is a frame mount type, so the trailer end has a bracket that boths to the trailer and a quick release pin so you can remove it.

Pete