Check seating to crank height at some stages our hips clunk when doing the cycle motion i noticed it when designing mine....i used the same back end but put a bottom bracket in it and a 3peice chainset an cut the crank arm off then ran a chain off it to the front cranks gets rid of baggy chain needing chain devices with roller wheels that create drag and noise..

It looks like a promising start. Have you made any progress?