Re: B&C adjustable medalist stock mods
Thumbscrews no, flushcups yes, but not in that model. The A3 or Light tactical is also a medalist, I drilled holes and epoxied in, things of note, I hit aluminium about 1/8" into the forearm and passed completely thru the aluminium before attaining proper depth. This did not concern me since I only did one side near the end (minimizing leverage on the area) and was installing a tight fitting aluminium cup. Where I suspect there will be a difference is in the buttstock, mine was hollow, I doubt yours will be, avoid the areas directly in the path of adjustment hardware and I suspect you'll be ok.
I would think thumbscrews would be as simple as finding or making some that match the diameter, pitch and shank length of the factory screws, and possibly shimming or lathing them to match the contact area under the head of the factory screw's profile and diameter.