Very interesting. I had a complete 'mare at the York NEFTA Hunter shoot on Sunday, with my old lazaglided 77K. I took the trigger unit out last week to fix a jammed safety catch, and had trouble lining up the front two stock screws. This stock is a CS800 with an extra deep forend, so a semi FT type, but it does have the single bolt through the lug, and no screw in the rear of the trigger guard. Now I got one bolt properly aligned but couldn't get the second one. It was ok before the strip. So on Sunday, after taking the rifle strait from the zero range to the course I noticed that bolt had come a little loose. Tried to tighten it but it would just have stripped the thread if I did it any more. I started off pretty well, knocking down quite a few, but then the wheels came off big style. But the wind was so bad I didn't even think about that screw. I bet it was that, as the latter half of the course I was convinced most of my shots were going very high.
My other main springer, a 97K with a regular V-Mach kit, in a GinB stock, had a zero shift issue on the practice range the other week before the springer championship at Anston. That time I simply tightened up all 3 screws, a quarter of a turn, and it was back, bang on zero. They weren't loose, but I'm sure that little extra tightening did the trick. The GinB stock however seems to have spot on holes. It's the CS ones in my experience that are a bit off.
Both the above stocks have no screw into the rear of the trigger guard but I can't for the life of me see why the lack of a screw into the trigger block is going to affect anything, IF the action is securely fixed in the stock by the other bolts.