I just purchased the Cardinal for XP11  through Xplane.org and the fixed gear model flies just fine, but the RG needs a lot of right  rudder trim in order to fly to fly level.

The plane wants to bank to the left. Is there a fix for this? Thanks

This is probably engine torque effect. This is one of the reasons I've never been able to embrace XP - as a real life flying Instructor I've never seen real aircraft turn themselves inside out like they do in XP. Many claim it's realistic, but it isn't to the extent modelled in XP.

I agree, the RG  version has this problem, but the fixed gear does not.

I have many real flight hours in both, as well as other single engine aircraft.

I believe there is a problem with the flight modeling that needs to be addressed.