Increase Ail
decrease or take out elevator
adjust rudder throw till the airplane has good snap speed prob med or high rate on that design.
adjust c/g back for the pich problem along with elevator input adjustement
without these adjustments you will not be able to do this manuver
you will also find your other snaps will improve also
ail should be between 15-18 deg throw 10-12 deg elev throw ....may-be none on the downline snap
hope this helps ,,, let us know !
Bryan