Thank you for the replies so far.

The stock itself is just a high quality polymer, but it has an aluminum rib in the forearm of the stock, so the threadsert would be actually placed in the aluminum. Different stock cost would demand I just go with a PIG saddle.

The M-Lok is an interesting and seemingly ready-made solution, but would require a different head, since my current one uses a standard QD plate rather than the rc2/q2. Would likely still have to drill stock unless the holes line up with current sling studs (which would also make bipod use another problem). I suppose if I get a different head (likely a wise course of action) the M-Lok would be more attractive).

Wonder if I can just rig up something similar to the PIG saddle, or if I should just save $ on the materials and frustration.

Thanks for the ideas so far. If I end up doing a DIY, I'll be sure to provide a write-up in case anyone else is going for a similar solution.