I actually considered this as a joke in the previous comic, but thought "NO! By golly, Tedd is considering actual, serious uses for helping out his friends, and that is not where their head would go in that moment!"

But then I realized it could still go there, so here we are.

"So... What about Tedd imagining Elliot in undersized clothes when the actual spell probably doesn't work that way?"

Because it was at least still the spell being suggested by Kevin, and Tedd in that moment didn't fully process why they were picturing it working like that.