On a balsa trainer of .40 to .60 size you can't go far wrong by using a protractor and putting 15° up/down in the ailerons and 20° on the elevator and rudder for low rates.  But I really don't know foamies and I hesitate to give you something that won't have the authority to recover from a loop.  It depends on the dimensions of the control surface vs. the rest of the wing or fixed surface.  Which is to say, the maiden flight should be careful.  As it should be with any model. 

Have you tried on the electrics forum for an owner of the same model?  Maybe ChuckW can set his up on a table and give to the at rest vs. fully deflected measurements with a ruler from the table-top?</p>