I believe I read somewhere that I need to calculate the mass of the basket, motor, etc, and subtract it from the internal volume along with bracing. 1. Some one listed it before, but I cant find it. What is the area for the magnet,motor of the 1503? 2. How do I calculate the flange on the driver? I saw on the blueprint sight 8.5 in. Is that 8.5 x 8.5 x 1??