I think that Glyn's questions are appropriate. Where does your shoulder hurt? Does it radiate into your arm and hand? Is something like the seat belt lying against it ? Are you holding it in an uncomfortable way, or supporting your self with it? Does any thing else hurt too or feel weak or numb? Something as simple as moving your bill fold from one pocket to the other or installing an arm rest or changing the angle of the seat, especially laterally may make all the difference. A good physical therapist or trainer or some insightful physicians can be a great help. Probably a few of them are Cobra folks and would be glad to just look (esp. if you offer them a ride in it while they are looking
) Also listen to your body, with a little thinking and experimentation it often will tell you what the problem is.
Rick