Ah, thank ya - that's my old show mare, who's been retired for 8 years now to the broodmare pasture. She is a doll, though.
I am not an expert on over fences by any means, but this is how I was taught to ask for leads over fences, and it works for me.
1 - if you want to stay on the same lead, drive your horse to the base of the fence. They are less likely to change leads. The opposite applies if you want them to change leads - let them leave a bit long.
2 - as you are going over the fence, weight your outside stirrup. If you want the left lead, put a little more weight in your right stirrup. If you want the right lead, put a little more weight in your left stirrup.
3 - this one works the best for me, especially if you're horse isn't that sensitive to weight cues. But, you have to have a completely independent seat and hands. As you are jumping, you can pick up on the inside rein. So if I want the left lead, I will take a light feel of my horses mouth with my left hand while in the air, and tip his nose slightly that way. Opposite for the right lead. It works best if you are using an automatic release, but it can still be done with a crest release if once again your seat is independent from your hands.
Best of luck, and you have a very cute boy. Let us know how the shows go, and your progress with him.
Oh, and in another thread on flying lead changes, it goes over some of the basic moves your horse needs to have to do a flying change. Even if you're not comfortable enought to try to teach him how to do it on your own (completely understandable), you might work on the prep work. It would help you with your flat work and control and balance between fences, and if you ever got somebody to help teach you and your horse, you would be ready for them!