My arab has always been downright fussy in a bit. He is fantastic in a hackamore that we use for riding out, but dislikes anything in his mouth.
I had tried single jointed, french link, oval mouth, mullen, 3 different JP mouthpieces, KK Ultra, and he was clearly irritated by them all. No seeking contact, incessant chomping even on a light rein at the walk.
I recently bought a Myler forward tilt ported snaffle, and he likes it much better. I also bought a Korsteel pelham with a smooth gentle port and use just a snaffle rein. He is a bit heavier in that one, though I’ve not used it in a few weeks because I hate the web reins on that bridle.
Apparently he just hates anything on his tongue. If I have the time to get him back to second level and can continue up the levels, I don’t know how he would ever handle a double. It just may not be an option for him.
Myler does offer a trial program. I got mine from Cheshire Horse’s ebay store. They said they would still take it back if it was like new, and would only charge $1 per day if he chewed it all up. The pelham I found for $25 on ebay. If I ever decide to show in it, I’ll have DH cut the shanks off to make it a ported boucher. The mouthpiece is dressage legal.