Whatever rudder roll couple is caused by dihedral, you could expect anhedral to do but in the opposite direction for the roll. How much? About as much.........

There was a $40 trainer sold for a month or so last year. Basically an LT-40, EagleII, etc etc but only $40. One of our guys got a dozen of them and we all slapped them together. A couple of us did the wings with anhedral. Easy to do since the wing joiners fit so slopply you could do whatever you wanted with almost no effort except for the rib matchup. Mine fought every turn the pilot wanted. Add rudder and it'd fight harder.

How to predict how much of what is going to happen with your combination of random parts? WAG