Hobie,many top shotgunners look more like Dilbert than Twiggy, Hobie.
And personally, I've been called many things in a long life but never "Skinny"...
Bad technique, form and fit are the culprits 99% of the time.
Fit, there should be a couple fingers' width between nose and thumb, and enough drop that one's eye lines up so little rib and receiver are seen when mounted.
The stock should fit nicely into the pocket just inboard of the shoulder joint itself. Do NOT mount on the joint or arm.
The heel of the pad should be even with the top line of the shoulder and all the pad having the same amount of contact.
The toe of the pad shouldn't dig in NOR not touch.
Form, lean well into it. Nose over toes, as they say. Use the firing hand to pull the shotgun into the pocket and use the support hand to push the forearm away a little. If the gun were rubber, you'd be stretching it betwen your hands.
Stay well behind the gun, not alongside it like a rifle shooter. This means the recoil goes into the whole upper body to spread out the energy and the spine acts like a spring, mitigating recoil.
Use the lightest loads you can find or make to get proficient.
Finally, there's no real difference at target between 2 3/4"and stronger loads.
I use reduced recoil 8 pellet 00 and have few issues with kick.
HTH....