I've had short transoms and tall transoms. Owned each of the big three motors at one time or another. I've also played around with transom heights (esp with the ProDrive) and seen gains from heights well off the recommendations.

I'm converting my transom from TT to ST for a new GTR. In doing research for the work I found out Gator Tail measures their transom height on the 20° angle. MB and PD measure height on the plumb line / T-square. So that means a GT tall transom is 18.5" on the plumb, whereas MB and PD are 20". GT short transom is 14.125" on the plumb (15" on 20°, they say 15-16" is acceptable). MB and PD ST are 16".

Who cares? When running the ProDrive, I dropped the transom height from 19.5" to 17.25", the boat gained 3mph (and no, I'm not recommending PD owners run out and cut their boats). How much performance could some of us be leaving on the table by pairing a motor with a transom not measured for it? Are the manufacturers' transom recommendations the best for every boat? You guys must have some experiences like this. I wish I could spring for an Atlas hydraulic jackplate and dial in the best height.

There are a few that have done this and have seen gains. I have really been contemplating it, myself. I really think I have a bad transom angle....more angle than required.

With a wrong angle, the trim may not go up or down quite as much. But I think you're getting at the distance from the bottom
of the transom to the prop. The wrong angle makes that prop closer (steeper transom) or farther away from the transom bottom than mfr designed. It might mean more cavitation / less prop bite.

One thing I will say about having the larger angle....my lower unit will root like a pack of wild hogs! It will dig deep and power through some "stuff" that leaves others looking for airboats and tow straps.