I think it's the size of the transformed-MC that's inconsistent; in the pages at the end of c16, he looks to be even larger than tMC... in c8's combat scene, everybody else appears to be mostly the right size relative to each other, other than a massively oversize tMC. See also c9p13 where he could probably fit Riko into his mouth without trying... there's also the incidents where it drops into the 'silly' style where sizes are artistically distorted. Eh; I'm just chalking it up to artistic liberties and inconsistent transformation.
It's kind of like in Iruma... I'm pretty sure that Clara's actually taller than him, if she can stay non-SD for more than one panel at a time.