I thought transom tie-downs were designed to keep the boat from bouncing up and down on the trailer (i.e., to make the trailer and boat move as one object). The placement in the picture would not accomplish that as the boat could easily bounce around when hitting a bump. I'd want my transom straps as close to vertical as possible; I believe that is what Boat Buckles are designed for.
Also, as mentioned previously, in every case the strap is either rubbing against the boat or the trailer, which means will wear pretty quickly.
Of course, bouncing around needs to be avoided. But that's not the only purpose.
A well designed "system" includes both bow and transom tie downs. They must ensure that the boat cannot move forward OR back. On the bow, I'm not talking about a winch or a safety chain, but a true bow tie down.
Often transom straps end up angled like the ones in the picture above. It is what it is....the design of the trailer forces that to happen.
As a trailer boater that was rear ended at high speed while stopped at a traffic signal, and thus causing the boat to "bounce around" (understatement), I consider myself an authority on the subject.
Over the gunnel straps are useless because they don't address the forward or back movement.
Retractable straps are useless because you never know when they will fail because of constant submersion.
Ratchet straps are iffy. An unexpected force can cause the mechanism to fail.
The only transom tie downs I will put on my boat are quality buckle straps that are equipped with a sleeve to protect it from the boat's bottom, plus a cinch to constrain the buckle.
Anyone can say what's good or bad, but until a situation comes up where you really need them, you may never know.
