And he seems to have quite a few buttons - dressage buttons !!

SO of course I am exploring the possibilities, probably going into the western dressage direction.
BEFORE I START - TEETH WERE CHECKED AT PPE, IN FACT MY DENTIST IS RECHECKING IN 10 DAYS, HE HAS BEEN SEEN BY MY CHIRO/ACCUPUNCTURIST, FOLLOW UP MONDAY.
Here is the problem: Apparently he was ruined as a youth by a "German " dressage trainer back in his home state (out west), and he became a very bad boy, rebelling at contact by violently throwing his head and,as I understand it,standing up tall...... Not much was done with him until last year, when he went to a home who worked cows with him, trail rode, competed extreme trail, etc etc..... He was ridden Californio style, big bit, no contact, romel reins, totally off the seat. Very cool!!
So we have been searching for a bit he will accept that is legal. Bean snaffle - throws head, doesnt stop. French link the same. Pellam with bean - better. Then a local trainer suggested a flat, three-piece with roller, mik-mar pellam. We ride with four reins, but 90% of the time off the snaffle position. HE LOVES IT. Actually beginning to lean on the bit rather than hide from it. He reaches for it. His body relaxes.
http://www.mikmar.com/bit-pages/pelham- ... inted.html
But it is an illegal bit.
So, tried a short shank lower port correction bit, since it only "breaks" in the same fashion as the MM. He is totally intimidated. Then, a short shank with a fat copper roller bean - not any better.
Back to the MM this week, and within two rides, again, fabulous.....I think he likes the stability and weight of it.
SO I am seeking suggestions.
Our plan at this time is to keep him in the bit for a while, and maybe try something else later on after he is more comfortable with contact. But what to try?
Right now I am not comfortable going bitless, so please offer other suggestions.
TIA!!