Just using the standard exported SK_Mannequin character does actually make IPISoft crash. I explored this solution some time ago, and ended up modifying it a bit by removing the ik joints the standard UE4 skeleton has. Since i usally have to bring it through MotionBuilder, it also includes some retargeting. I've documented some of this workflow here (in case it's of use for someone):
https://www.youtube.com/playlist?list=P ... -hvniY8eyPIm very interested in feedback on this process, since i havent really been able to find something similar. So please feel free to pitch in with additions/improvements, preferably by commenting on the video, where i usally answer questions.