Every horse is different, my horse was in the same position but was completely fine with the saddle, if it is an issue maybe consider getting him rebacked. Good luck!
They would’ve been broken in a stock saddle, and then ridden in a track pad or stock saddle throughout pre training, a saddle would be no issue :)
I have an OTTB. He raced for 5 years. He accepted his sadle with no problem at all. Just make sure the saddle is properly fitted because you don't want a situation where your saddle causes discomfort to your horse. Good luck and congrats! OTTB's are great horses!
They use saddles on the track. They are smaller and lighter, but saddles nonetheless. Ottb's are saddle broke, bridle broke, broke to ride, but they are trained differently. It's not the "breaking" that is the problem with these horses, it is teaching them their default gate is no longer the gallop.
Read books on retraining ottb's, there's a good one by New Vocations on Amazon.