It's easier to make a running braid stay up higher if you stand on a stool on the opposite side of the neck to braid it. ;)
A woman I used to work for had a client with a Friesian/Arab mare that had massive amounts of hair, so any time she was in for training I'd have to running braid it before every ride. I got pretty good at them, lol.
Looks great! Like strange said, if you want to get it higher, stand on a mounting block and keep your hands at the very top of your horses crest. I have done french braids right on top of Casey's neck before, it looks quite interesting- although I wouldn't leave it in other than for riding.
This was my first running braid - I realized after that it was a bit too tight. So far I've only done them when we're going on a longer ride. She has such a long wispy mane it can be a real pain! (last pic is her mane loose, I'm sure you can see how that would get in the way!)