I just got my cowl mounted tonight - my prop hub is 5 and 1/8th from the firewall - of course I'm running the 26 on mine with 3/8 in standoffs, but still - the cowl could slide a little farther in on the fuse, and a little farther out.

The website says the 40 is 5.4 inches ~ 138mm where the 5 1/8th is about 130mm - so it's really up to you how you have scott cut them.