i’m really glad you’re getting him neutered! males can be neutered when the testicles drop at 3-4 months (so within the next month or so for Henry)… the behavior might start getting a little ramBUNctious at that point. after the neutering, allow about a month for a decrease in hormones.
another thing tho, you do need to be aware that rabbits go thru adolescence which is different than hormone-related misbehavior… so, even with neutering and the absence of hormones, he may still be wild and a little bit destructive up to (or beyond) the first year. it is strictly age-related, so it would happen with or without altering… some bunnies get it worse than others, so you might not even really notice. but don’t be surprised if he calms down after neutering, and then a couple months later some pesky habits return. it will pass.
this is a good article that describes the difference (better than i can…) http://www.rabbit.org/journal/3-3/age-related-behavior.html
another good one http://www.rabbit.org/journal/2-9/rebel-with-paws.html