Okay, those materials aren't easy to come by in Arda, but sometimes the Corsairs will take special requests. For now it sounds like he'll be stuck with the 3 he has.

Onto flight!

Placing a flight speed limit isn't an exact science or bathed on "real math" but we still try to make it comparably fair.

Considering his size / abilities vs some of the other flying creatures we have here, I'd be comfortable giving him a max speed of 7-8 "days by foot" travel.

That means if it takes a normal person 8 days to travel to a destination, Corbin in crow form could make that distance in only one day.

Are you okay with that limit?