Wow, 4 year old horses do 3 day eventing? I thought it would take much more time to train Grand Prix Dressage on a horse than a mere 2 years (unless you start riding the horse as a yearling, then they would have 3 years to train for it.. which still doesnt seem like enough time) and I always thought jumping a horse before the age of 5 was just a bad idea in general because of waiting for the knees to fuse completely. I know they fuse when they turn 2 years old, but I thought it was a big no-no to do heavy/strenuous physical activity until they were 4 or 5.. and if he is a 4 year old already jumping 3+ feet... when did he start jumping? You said this was his first Cross Country course, but by the looks of it, he has been jumping for a long time prior to this (because of his form and the height of the jumps)
Blargh.. don't mind me, I just tend to get concerned for show horses... they just keep training them younger and younger.. before you know it, they will be racing and betting on weanlings, putting those huge clogs on Tennessee Walking Horse weanlings, etc etc.. Im not griping at you though, just generally at the horse industries :).
As for your pictures.. I really don't like how the bit is sitting in his mouth on the first one, it looks like an eggbutt snaffle that was pulled almost completely out of his mouth on the other side (or it is too large for him) If he (or you) have a tendancy to pull the bit through his mouth, i'd consider getting a full cheek snaffle. They come in all styles (Normal, Happy Mouth, Slow Twist, Quick Twist) and the large.. err.. shanks? On either side will prevent it from going into his mouth and if anything help him steer a tad bit better because the shanks will actually push his head if you pulled hard enough on the other rein.. if that makes sense (i just got up, im really groggy)
In the second picture, it looks like you are coming out of the saddle. Almost like the horse jumped too big (even though he looks awesome) or that you werent expecting the sudden impulsion from behind. If you grip your knees on the knee rolls before the jump it would prevent this from happening. From what I gather about you though, I don't think this is a huge problem for you, I think this was a one time flook and the picture just so happened to be taken at the worst possible time. I just figured i'd point it out. If I recall.. Cross Country is a lot like barrel racing.. form and style doesnt matter, its all about speed and precision (I.E. Not knocking over obstacles or refusing to do it)
Your horse looks very willing and athletic, you guys make a great team =)