Clouds - Bud Anderson gives a detailed description of a dogfight he had with a 109 at 30 to 35k feet. He was flying a P51. This altitude isn't seen very much in AH because the distances are so short and it takes too long to climb that high.
I did attempt an interception of what turned out ot be a p38 at around 30k. I was in a p51B. He must have been typing because I was able to get some shots off, but my closure was too high and I blew past, tried to turn, but had almost no control and went into a spin. I noticed that he also lost control when he reacted to the hit sounds - quite a comedy - both antagonists spinning out.

By the time I recovered he was out of sight (later I got a kill message). I was really surprised at the lack of control at that height. it seems more severe than I expected from the descriptions in Anderson's book. But probably I'm just not used to the handling at that height.