OP: what stock(s) are you using? That would help...
2 solutions I've stumbled into, that work for my MPA/XLR, after trying a Sykes clutch and Grey OPs nubs, etc.:
1) MPA side rails work very well on my MPAs and provide a long continuous shelf for support hand, and
2) A low profile enclosed forend provides similar continuous coverage for support hand pressure/pinching, like the XLR envy pro full cover, and you don't need doodads bolted to the sides if your barrel is covered.
Those are the 2 competition stocks i've really figured out for my preferences, but on my manners, it's still a sykes clutch in a custom swivel port (wish it was closer tho) or support hand on top of front scope ring pressing down onto barricade benchrest support bag, lolol.
For me, I'm finding that a fully enclosed forend is a good feel and quick solution for my support hand to settle wobble without reaching for a specific spot.
Really like my XLR Envy Pro and MPA side rails, and the JP APAC looks nice as does the AI AT-X full rail, but I've not tried them, but YMMV, etc.
Depending on your stock, like an MDT, you could always just run a side weight or 2, which also serve as easy thumb rests.
Just another gear rabbit hole to figure out I suppose...