Just give him two identical hides on each end and he should be fine. My (approx.) one year old Milks are in 15qt tubs that appear too large for them but they feed and thrive fine and when my BPs were much smaller I kept them in 41qt tubs with a couple hides and they've never had issues either.

Also, yes they do calm down as they age but be sure you're handling him occasionally also. If he's left alone as he ages he may still be aggressive, as I learned with my four year old normal male. Under care of his previous owner he wasn't handled at all for about three years, was tossed a few mice and had his huge tank cleaned perhaps twice a year (filled with filthy sand). Due to him never being handled, he was just as aggressive as a baby BP. A few months, several nips, and many hisses later he has calmed down a bit but I doubt he'll ever be a sweet little BP.