Mossberg's other idea is stock spacers to change the angle of the entire buttstock. The system can raise it up to 1/2". Not sure how it would feel on the shoulder, but at $20, it's an inexpensive option.

Stock Drop Spacer System
For a better fit and better scores !
Considering that one gun does not fit all shooters, Mossberg® designed this new “system” of Stock Drop Spacers. It’s an easy and efficient method of bringing the comfortable fit of a custom stock within every shooter’s reach.
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Spacers are inserted between the stock and the receiver.[/align]Each set includes (4) specially contoured nylon resin spacers. These enable you to raise or lower the vertical angle of your stock in controlled personalized increments, from a ¼” overall drop, up to a ½” rise. Spacers fit all our 835® Ulti-Mag® and 500® pump action, wood or synthetic, 12 gauge shotguns.

Spacers are marked (these were painted) for raising the comb +3/8", +1/4", +1/8", or lowering the comb -1/4". If you wish to raise the comb 1/2" (1/2" is the maximum Mossberg recommended height) insert both the +3/8 and the +1/8" spacers.

"LOP" a little short? Insert both the +1/4" and the -1/4" spacers to increase the "Length Of Pull", it might be just enough. [align=center]#95091.....$17.99 suggested retail[/align]