So I made this AGES ago, before the new pelts were introduced, but I just found the file and figured it might be dandy for others to know about? So what happend was that at some point we realized what pelt you wore under the crow spell, decided what size it'd get if you prayed at the twin gods.
Default pelt makes for a very smol crow, but the monarch/butterfly pelt gets you a giant birb. You know. For science!
I don't know if this trick corresponds the same way to other animal spells. We didn't get that far. And I'm also not sure if this is like common knowledge by now, apologies if it is!