Yeah I've noticed that the form is too big to fit through small passages and tunnels that a human form can fit through.

I know you can change back and forth unrestricted, but it's a hassle to revert and revamp just to fit through a corridor.

Really puts a damper on my dungeon crawling to feed and develop my skill tree.

Unfortunately crouching wouldn't help since it doesn't shrink character's collision box. :/

It is a problem...there's something sinister about creeping through dark dungeons or mines sneaking up on people till you crack your head on a door frame, or your shoulders won't fit through a passage way. Try the fluttery bats power.