Are you using PMD's? They were designed to help with this very thing I think. If you're not using PMD's and everything is being stored in the CR2, you're going to see the file size jump due to the large number of morphs, so in cases like that - 31 megs is probably normal. Heck, it's probably pretty low.  If you're not using PMD's try saving out a version that does and compare the file sizes of the CR2.

 

Personally, I don't really care how large a Cr2 is in file size as long as the figure works. It may take longer to load but that's a trade off I'm happy to make if everything about the figure is flawless.