I have an Sena case and a Arkon mount (CM720) for my car along with iGuidance/BT-339 combination. I don't think a Sena case with a belt clip will work because it would extent the PDA out to far for the catches; hopefully you don't have one.

The Sena case I have doesn't have the belt clip though the case in itself causes the PDA to barely stay snug. If I were to go down a very bumpy road it might fall off.

So far I have been doing regular street driving and it has held on.

I have contemplated trying to make some kind of fix to my Arkon holder to keep it more secure. Maybe just as simply putting a rubber band across the top. If you like I could perhaps attach a picture of it? Good luck!