I like the idea, but the implementation is glitchy beyond playability. Half the time I change sizes, one of the characters gets nudged to one side, desynchronizing them and making it pretty much impossible to beat the level. Sometimes, I change side and just instantly die for no reason, too.
I was able to beat the first level after a bunch of trial, but got frustrated in the second level.
Jam games don't need to be extremely polished, but this is not really functional.
I like your use of the limitation, though.