I also have experimented with them quite a bit they are my favorite deer bullet in the Triumph and the Omega.
I find if I push them over 2,000 FPS The group open up fast, As far as terminal results are concerned I have never found a point at which they will break up but the highest FPS I have checked is 2200. I tried all three sabots that fit well in my gun and the Long black Harvester [over 300gr] works the best the other two the MMP HPH 24 and the Short black Harvester [which shoots a lot of bullets the best in my guns] shot an inch or more larger groups.