Thanks guys. This thread has provided some humor while trying to figure this out.
I tried poking again but this time with a smaller phillips screwdriver. Bingo! Found one of the holes and the other 3 1/16" from the first. After some effort with the different size phillips, resorted to a straight screwdriver and that did the trick. Maybe straight screws were all that a PO had laying around at the time, who knows. Also, no glue either which was a relief.
The LOP measures at 13". My 12 gauge with pad is at 14 1/2" and feels a better fit. I'll probably shoot for about the same on the 99, perhaps even a smidge more.