Don't worry about stalling a model biplane!
Setting one up for the stall regime, which is an insignificant part of the flight envelope will degrade all the other areas where the plane is going to be spending all its time anyway.
The difference in angles between top and bottom wings was done for full-scales.
We exceed all the normal parameters of full-scales with our models.
If you like the way it flies with 0-0, leave it there!