A clubmate and I have both suffered POI shift with our 97s over the winter. He shoots a factory stocked (wood) 97KT with an SFS tune, I shoot a factory sporter stocked (wood) 97K with a V-Mach kit – so shift affects not just Venom kits and custom stocks.
Just to add something else into the mix ...
From the BKL website, their Drop Compensated (D7) mounts have “7 thousandths per inch of drop compensation, which equates to 24 minutes of angle at 100 yards” i.e. there only needs to be a VERY small change between front and rear scope mounts to induce a noticeable POI shift.
As our POI shifts have occurred over the winter, and mine has been very repeatable – adding and subtracting the same amount of clicks each time - this has led me to think thermal contraction of scope / mounts / action may be playing some part.
If it's true that TXs have no shift, the main difference with a 97 is that the scope mounts are usually across both parts of the action whereas with the TX, it's just one piece.
I found these pics in one of Ninja's stock making threads, check out the position of the mount ...