A new GM6 Lynx recently joined my Windrunner in consuming .50BMG ammo. The guns could hardly be more different.  The Lynx is long recoil semi-auto weighing 27# with scope vs a 37# bolt action with an extremely efficient brake.  My repaired shoulder could only stand three rounds of factory ammo before the hard butt pad emerged victorious.  I swore to not shoot it until it was wearing a Limbsaver on the butt.  Major props to Ian for shooting over a hundred rounds for the range video.  The factory shoulder mangler was glued and screwed to the butt and had reliefs molded in to clear reciprocating parts.  Factory pad on right.  The LOP made it impossible to go with a slip-on pad.  Bolt at rearmost travel:    The Limbsaver was 'inletted' via a few different Forstner bits.    The pad had to be cut to allow removal of the bolt spring before gluing and screwing it in place.  
I then was able to shoot fifty rounds without any shoulder pain.  Picture of Lynx next to mousegun at range:  

Very cool I’ve watched Ian’s Lynx videos in the past, but of course I had to watch them again Beautifully made  firearm, that I wouldn’t hesitate to add to the collection. Excellent acquisition

It's fun to shoot, but it has noticeable recoil due to the design.  I found the folding fore grip was useful in keeping control.  Just loaded fifty more rounds of AP with a lower powder charge to see how that goes.  Might have to adjust brake to bleed off less recoil.  At the rate I'm going through ammo, my components may only last me another ten years or so.

Very unique rifle.

As for that buttpad, seems like a ridiculous design oversight by company that made it.

Would be cool if 3D printing could make a mold that could be used to cast a silicone part and then possibly a rubber part once finalized.

Your work around makes good sense and good use of available tools.

For a factory option I would think a buttplate that had something like a rail for interchangable/modular buttpads with room for proper relief would be welcomed by most users.

If you're ever near the CA border, I would gladly drive to where you are and bring ammo! Just for a chance to shoot a mag or two through it.

That is by far the coolest bullpup made.

`@uglygun
The factory pad seems like a pre-3d printer solution that trades comfort for durability.  The mold for the original pad couldn't have been cheap.  Nowadays, you could print something with the same exterior and inletting with internal honeycomb to absorb the recoil for a lot less.  I am mystified why there are no other butt options offered at the price point of the gun.  Hell, they could charge a few hundred more for the equivalent of my modification.  It would be worth it, given that each mag is priced around four hundred U$.  I dunno, it must be a Hungarian thing.