I have no experience with the ST rotor. To do a proper job and not break the straw up to much replace the spiked rasp bars in the "concave" front 2 module areas, install 4 small wire modules in the front and reset your concave zero. Then install your round bars in the rear separating "grate" area. You could try it with the spiked rasps and see if the straw is long enough for you, if not you may have to switch out more rasps to the standard ones over the rear modules.
Depends on how hard the wheat is to thresh out of the heads if you can get it threshed out with the spiked rasps in the front then you might not have to change them. Depending on crop,weather and other conditions.