This won't be of much help, but I know that I've seen a Lapua action in a thumbhole stock before. Unfortuntaely, I don't remember what kind of stock it was. I saw it over on SH last month, so if you wanted to peruse the PX over there, you might find it. It very well may have been the Boyd as I know that it was a semi-custom build, but I can't be certain.
I myself use the XLR chassis and have been extremely pleased with it, but thumbhole stocks have just never been my thing.
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