Hi Joel
Which hatch design did your truck have Round or Rectangular? Round would have been something about 26 inches.
If you can not tell from the patch which it was what year do you think your subject truck is? From the CMHS web site it appears you are working on a 1942 which as I understand it would be the rectangular metal hatch.
I have some details of the round style 1945 vintage on my website
http://www.canadianmilitarypattern.com/Posting.html I also have my hatch and all the hardware off my truck so I can provide any photos or dimensions you need if you are looking for the round style.
Cheers Phil