When I jump, on the approach, I just have a light contact, and don't really have a lot of slack at all, because if I drop the contact, my horse will stop. But it's just a light contact. Then when he takes off I push my hands forwards to maintain a slight contact whilst still allowing the horse to stretch. How much of a release you make in the air really depends on the size of jump, eg if the jump is only tiny you don't need to give a lot because the horse doesn't have to stretch a great deal, but when they get bigger you will. I find it always very useful to have someone watch me jump (for safety reasons as much as anything but they can sometimes see more than you can feel) because if I don't give enough and hang onto their mouths, one horse jumps really hollow; the other one bucks!
