Hey, I'm an artist. I'm mathematically impaired also. (and I have a Philosophy degree to prove it!)
If you want, tonight when I get home, I'll measure the distance from the negative carrier to the end of the bellows/lenscone with my 5x7 enlarger with a 210 componon-s on it, with an image size of 9.5 inches on the long side.
I assume your bellows extention with the 180 would be slightly shorter.