My youngster Toto is just coming up to a year and has never been a problem with his rugs, just stands there. have you tried feeding him while he gets his rug on. If he has the Arab skin it could be that he is extra sensitive. Are his rugs a good fit, Toto is on his 3rd as he has out grown the others so quickly. I would suggest just taking your time and try not to make an issue out of it but reward him when he behaves. As it summer ( well suppose to be ) try an old towel over his back after a grooming session. just put it on, leave a few seconds, take it off and reward. work up slowly to a light rug being put on without hitting any part of his body with the straps. The first time any of mine are fitted with a rug I fold it , lay it over the back, unfold the front and fasten then the rear just chatting away all the time. Can anyone help you, he may behave better. All horses have some form of hang-ups so don't worry.