Red,
"............Here's a question - Many shotguns and rifles have what they call a cast to the stock. The butt is angled left or right from the bore line. This is to recoil the gun away from the shooter's face. Too much the wrong way can cause it to shift into the cheek ....."
Not quite.
Stock cast has nothing to do with recoil in a shotgun (I do shotgun stock fittings). Since your eye is the rear sight on a shotgun, correct and consistant head placement on the stock is SUPER CRITICAL to being able to hit moving targets with a shotgun. "Cast-on, and cast-off of a shotgun stock are done to change the stock fit to match a shooter's shoulder width, and face contours to that shotgun, so that your aiming eye is alinged with the bore centerline when your head is level. Having your head level helps with how your brain precives distance to targets moving at an angle to your line of sight.
The angle of the top of the stock is what has the most affect on "felt" recoil. That's why some target shotguns, most notably the Browning trap guns, have a forward slope to the stock. As the gun fires, the stock angle moves away from your face, not up into it like most field shotguns do with the revese slope they have to the stock's top edge. Guys who use field guns for long sessions of clay shooting often get brused, sometimes even cut-open cheeks because of the stock's top angle going into, rather than away from their face.
The Trail XL's have a "cast nuetral" stock. In otherwords they are centered in a vertical plane so as to be ambidextrous. But, like the Browning trapguns, the stock comb top edge rises slightly toward the butt. With the strongest recoil being the oposite of a centerfire or shotgun, forward recoil during firing will bring the Xl's stock up into your face.
I found that, because of the high rings Crosman uses, sitting on the Weaver rail, it raises the scope so much, I couldn't get a good cheekweld without putting a pad on the stock. With the pad at the correct height to give me a good cheekweld, the recoil is much less noticable.
The headache could be from a loose cheekweld and getting hit by, rather than snuggly "ridding" the stock during forward recoil.
And, I think the "pinched nerve" is also a good possability.
Paul.