For what it’s worth, I hunted Mr. Blondie last season in a Myler combi bit.
I’m not sure it was a whopping success. We had quite a bit of bucking at the canter for the first part of the season (until I learned that he was much happier with his nose stuck up some other horse’s butt–and we paired up with a horse was much happier having another horse’s nose stuck up his butt :D) Of course, the fact that pretty much the ONLY time he cantered was out in the hunt field might have had SOMETHING to do with the bucking…
We started out this season with an eggbutt Myler comfort mouth snaffle and a running martingale, and he seemed okay with that, although I didn’t have quite the brakes I would have liked (but I did have steering). I think the combi bit annoyed him. I had a similar experience a while back with a mullen mouth Pelham. It was a pretty heavy bit, and by the end of the hunt (only 2 - 2 1/2 hours), he would get fussy with his head. (A Sensitive Fellow, is our Mr. Blondie)
Mind you, we are generally at the back edges of a relatively small field, and we’re going over pretty uneven ground, so we (Mr. Blondie & I, at least) seldom get a really good head of steam going. I expect I would have quite a different beast if we were hunting over flat/rolling ground and having to deal with large groups of horses.
And Mr. Blondie is generally quite content to stand around quietly at checks and try to sneak some snacks. So our experience probably has little bearing on your situation.