Rear foot toe count isn't a surefire way to designate major vs. triunguis. major's can have three toes. You might wait till the animal is large enough to have additional morphological characteristics of the subspecies before making judgment on whether to breed it. Can't hurt to do that since the animal won't breed till then anyway.

The "purity" of captive T. c. major lines is questionable, anyway. Specimens from southeast Louisiana tend to look different than the ones I've seen in the Florida panhandle. Relatedness in such variable animals will always be relative when we're talking captive lines of unknown geographic origin.