My gelding can get VERY strong, so I get where you're coming from!
I put him in a kimblewick but like you, didn't much like it. The response was good, but there wasn't enough refinement. I didn't have the option of giving him a light curb-free aid before the curb chain came into action. He liked the mullen mouthpiece though so I tried him in a mullen pelham, and that worked awesomely - I still show him in it.
I wanted to put a grakle noseband on him because there's some really pretty ones [yes for looks not function lol, I don't tighten nosebands very much and he doesn't cross his jaw so it wouldn't actually -do- anything]. Can't have a grakle or a flash with a curb bit here, not at my level, so I decided to try him in a gag.
He hated it. Or rather, he didn't mind it, until the gag action came into play, and THEN he hated it. My horse doesn't like a gag bit. Every horse is different, of course, and what mine will resist and run through, yours might respond beautifully to. [bear in mind I now jump this horse in a snaffle at home and he is wonderful, and I can pull him up in it even if he's being a strong brat... he only runs through bad riding and/or a bit he hates... the pelham is his show bit still though because he turns and rates better and I have more stride control, plus he gets excited and is much stronger out]