Taking it to extremes might help you:
Imagine if you could add 200 pounds to the stock of the gun, then you fired it while it was resting on a bench by simply pulling the trigger - without putting it against your shoulder. The gun probably wouldn't move much, if at all.
Now imagine adding 2 ounces to the stock and doing the same thing - it would jump out of the rests (and onto the ground) just as much as it did before adding the extra 2 ounces.
2 pounds falls somewhere in between - as would the reduction in gun movement upon being fired, or recoil.
The force created by firing a gun is not effected by the shooters weight. Yes, a bigger shooter will be moved less than a smaller one, but the actual force created by firing the gun is the same in each case.
Just my 2 cents - hope this helps.
