I know we always talk about not running our outdrives trimmed too high because it is hard on the U-Joints. Does anybody have any actual measurement in degrees past which a outdrive should not be operated at speed. I would imagine that if you keep trimming up you eventually cavitate and lose all speed , but in the case of TRS drives which are already deep, what angle is too hard on them?

There is a spec on maximum length your trim rams should be extended. It's been discussed here in the past, but I can't remember it. BUP would know.
There are even some plastic spacers you can put inside of your rams if you want to make sure you don't trim too far. But the easiest way is take note of the indicator.

The trim tab has a specific measurement between the mounting bolt and the end of the cylinder when fully extended. An adjustment of the limit switch is dependent on that measurement. On our bravo 3 it was something like 22 inches. You can google it and I know it’s available

Watch the GPS and keep trimming it up until it starts slowing down!

Maximum trim ram pin to pin is 21.75"

For Mercruisers --- Bravo one - two and three and Alpha GEN ONE you set full trim limited at 21 3/4 inches center to center ram anchor pins

For alpha gen 2 that measurement is 20 3/4 inches

For Volvo Penta SX and DP and OMC cobra there is no trim limit for any sort of adjustment.

Also what can hurt trimming to high is air instead of water being sucked into the side feed water inlet holes of the outdrive

Also Prop blow out spinning the rpms WAY TO HIGH

Also for Bravo 3 and Volvo DP trimmed to high can put the back prop out of the water causing poor handling and hard on the rear propshaft in and out grabbing water for a jist.

Ill have to take a look at my manuals for the settings for the TRS drives.