Note that I qualified my statement with IF... I am glad to hear of your attitude.
If he's not currently backsore my guess is that it's not as much muscle related as bone related OR it's remembered pain triggered by some other pain when the saddle goes on.
But.
There are still other issues that are presenting themselves- if he has taken this long to gain weight I really am concerned about his general health.
If he has scars in his mouth I would ditch a bit altogether, and if you feel it's not safe to go without one, use a VERY gentle snaffle (perhaps a fixed ring double-jointed bit, smooth mouth, about 16mm- make sure it isn't a Dr. Bristol though).
If you're using a tie-down, get rid of it.
There's no argument here that some of his behavior is learned- but something is triggering that response and your job is to figure out what it is and fix it, then show him that hey, that trigger isn't here anymore and it's OK to be calm and quiet.
If he's not currently backsore my guess is that it's not as much muscle related as bone related OR it's remembered pain triggered by some other pain when the saddle goes on.
But.
There are still other issues that are presenting themselves- if he has taken this long to gain weight I really am concerned about his general health.
If he has scars in his mouth I would ditch a bit altogether, and if you feel it's not safe to go without one, use a VERY gentle snaffle (perhaps a fixed ring double-jointed bit, smooth mouth, about 16mm- make sure it isn't a Dr. Bristol though).
If you're using a tie-down, get rid of it.
There's no argument here that some of his behavior is learned- but something is triggering that response and your job is to figure out what it is and fix it, then show him that hey, that trigger isn't here anymore and it's OK to be calm and quiet.