The thing to remember is that every different limb design has an optimum brace height, and the bowyer or manufacturing company typically determines that brace heigh and string length.
If you are testing prototypes and trying to determine the optimal brace height, that’s where an adjustable riser comes into play. Taking the time to try different limb pad angles and using different string lengths is critical. You can check the string tension with an in line scale if you are so inclined, or simply shoot the bow and test the vibration level, sound, and speed.
When I’m doing a prototype set of limbs, I always start with a TD riser and do not shape the grip until I’ve determined the right preload and string length to maximize the limbs potential. Then I measure back from the string and mark the deepest part of the grip on the riser block at 7-7.25” , and shape my riser from there. If I want a one piece bow, I use the TD bow I’ve just fine tuned as a pattern for the limb pad angles and depth of the grip.
Kirk