41" x 8' pit need help with rack placement

hi everyone. i can not wrap my head around the rack placement if its possible or not.  I'm tring  to do 3 racks high. I'm trying to model it after a meadow creek ts500. they claim to fit 46-50 briskets that's my goal. racks will be made out of 1x1 square tubing . where i get confused is cutting the doors and having room if the circumference is 132 then a quarter of that is 32.5 . so 3 racks with 10" of space is 30" plus 3" for grate thickness = 33".  but if that's a quarter of the circumference it equal es the radius whit ch is 20" math isn't adding up please help