Actually though, although you could do little bit more, it is good that you aren't over releasing or perching. That is one of the biggest problems people have and if you get used to doing too much at lover levels, it is hard to dial it back. As someone who is having this difficulty, it is much easier to work on giving bigger releases over bigger fences, and having a nice moderate release over tiny fences than it is to fix a habit of over releasing over all sizes of jumps.
My biggest concern would be whether you would release enough with your hands over larger fences. You are releasing, but not much, which is appropriate considering you horse is mainly cantering over the fences. I think we'd need to see a vid. or pic of you over larger fences to see if you need to release more in general.