It is common for young bp's to explore and try to 'escape' when settling into a new enclosure. Be sure you give him a week of no handling so he can settle in, but it may take a few days to a few weeks before he stops trying to 'escape' and settle in. It is true, he can fall and bonk his head or even damage a vital organ should he fall hard, which is why it is important to have an enclosure that matches the size of your snake. My snake is over a foot long, and his tank is 12 inches high, very little room to fall.

The reason bp's fall so much is because they are ground dwellers, not tree climbers. If you want, you can add a branch or two (you can by them at pet stores, drift wood, bendable artificial vine, ect) which will give him more to hold onto when he climbs up the sides of the tank.