bitting question??

I a having trouples with bits to use on my horse. .
he is a very stocky 15.1hh station bred gelding a rescue horse and a very friendly soft mouth horse. .
i am having problems with trying to find a bit that i can stop in when showjumping as he turns into a very completly different horse when in the sj ring . . when i get into the rings hes just takes off and runs through his bit at the jump and as soon as he hears the bell he knws whats happening and start prancing and trying to canter. . im just trying to find a bit that i can bring him back into a steady canter and not gallpo aroung madly giving mum heart attcks =P
his problem is that he is very fussy over the moouth peice and will rear and go over backwards if he has poll pressure , have tried pelhams and dutch gags with 1 and 2 reins but still rears with the slightest pressure. .
i do showjump him in hackamore no problems with rearing unless im WAY too heavy but that doesnt really happen . . but instead he tucks his head into his chest and he cant jump with his nose on his chest all the time and when i let go of the reins or push on or both forward so they slacken to loops in the reins and stretches out his canter but still keeps his nose on the chest. .
he is very fussy over the bit and he doesnt have a very big mouth so it has to be a very thin mouthpiece. . it cant have nutcracker action as he can't stand them and tosses his head. . can't have poll pressure as he rears . . he is very good with mylers and loves them but still runs through them at a loose end here but the sj season has finished except for the odd winter series so have all winter to play with bits
so any help appreciated thanks

Your horse needs to be retrained from the ground up. It is possible his training was rushed and your trying to show/jump him before he is ready mentally to listen to you isn't helping him, or you.. Poor mum..

Having said that, I would suggest a simple snaffle. Find the right size for him but keep it very simple. D ring, Full cheek, O ring, whatever.. Go back to teaching him to flex, give to the bit, all the yielding exercises both on the ground and then mounted. Be sure he is solid before you try showing him or you will simply undo the work you put into him.

he is 7 and when got him as a rescue case we spent 2 seasons re-training him from the ground , dressage, and jumping he spent a season doing low level pony club comps and he just got bored at the same height. .
hes moved up slowly through the heights now im sjing as this my 1st season doing registed sj his too . .
the problem is anything that reminds him of his previous owners freaks him out someone did the " i watched the natural horsemanship video now i cant do it" training with him and it riuned him and you cant do any form of natural horse manship anymore with him . . even natural horsemanship ropes freak him you cant get near him with them as he spaces. .
we've got all winter to train with him. . we have had people suggest remouthing him with key bits and starting from scratch do you think this would work??

This tells me you need to start over COMPLETELY on the ground desensitizing him to everything adn building trust and RESPECT, if he is tripping out he does not see you as a leader but a predotor fix the problem on the ground and build from that in the saddle.

A bit wont' fix your problem it is just a bandaid!!

I have to agree with the above poster Peggysue completely. Sounds like your horse needs to be completely restarted and that his issues are from fear and lack of confidence, not at all from a need for a stronger bit.

I agree. Apparently someone really screwed him up so now he needs you to take things SLOW and put a PROPER foundation on him. A harsher bit is not the answer.