Some earlier communication between Bob and I:
I think he'll be ready for the 4-H 10-mile ride next weekend (17th or 18th). It's up to you which one of us rides him.
I definitely want Dig to do the 4-H ride. Have you ridden him with your saddle yet? I’m interested to see if he’s sticky/weird with you about that like he was with me on Sunday. Would one day be preferable over the other to come and ride?
Note: On Sunday, when I would go to move around, trot, or lean forward - Diego would throw on the brakes and totally stop. He was pretty tense and I spent a lot of time just walking him around in circles while I flopped around and moved all over as much as I felt comfortable doing.
I believe horses care more about your body language than what you put on their backs. The first time Surprise ever saw a saddle, I walked into her stall, let her examine it, and then put it on (no halter). I put on a bridle, led her out of the stall, and took her for a five-mile ride. To this day, she has never reacted to the saddle.
I'll probably try my saddle on him this weekend. I'm also planning a solo trail ride and a little cantering soon.
With Diego, when we were in Idaho and I was meeting him for the first time, I took him over to the trailer and tacked him up. He was fine, it was just him and I and, as far as I knew, he’d had a saddle on the week before (turned out this wasn’t true). We walked about 300 yards over to their round pen, again no issues, I turned him loose and all hell broke loose and he bucked around for a few minutes before I could get him to stop. That was NOT his first time wearing a saddle, and I had no prior expectations and had treated him like a broke horse. I didn't expect the saddle would have been an issue at all. Once he finally stopped, we had no further saddle or bucking issues.
Took him home, no trouble, no issues with the saddle or being tacked up. Never seemed to react again. Fast forward to June, I pull him out and go to throw the saddle up on him (it's been since early April since he was tacked up), and again he totally freaked out. My mom had a hold of him and they ended up going all over the yard, Diego was just a royal pain. He was also a little odd about it this past weekend, but it didn’t take much to get him to stand there and behave. I think he has a very sensitive back (or is sensitive ABOUT his back – two different issues in my mind). I’m hoping you’ll ride him a bit more in a saddle just because that’s what he needs to be used to for ME. ;) I’m also curious to see how he reacts to you leaning forward and moving around, like I was this weekend.
Sounds like I should put my saddle on him today or tomorrow, just to see what he does.
Update from later that day:
I put my saddle on, rode around the back yard with Anjolina, and then took him out on the trail by himself. As you suspected, he is more reluctant to go forward with the saddle. He sometimes backed when I wanted to walk or trot. He definitely didn't want to leave his mares behind.
We worked through everything without getting either of us upset. When I realized he wasn't going to do the entire trail ride that I had in mind, I made him walk forward and then turned him around on my terms, not his. He walked and trotted back nicely. We opened and closed the gate with a minimum of fuss both ways. I think he will be OK for the 4-H ride if he has a buddy or two. :)