BODAB,
Did you check your factory torques before you started your test?
Just finished tuning a load for a friend, his model 116 accustock was less than 20 in/lbs on the rear screw and only 30 or 35 on the front screw. Groups dropped from 1 1/2" to just a tad over 1/2" by tightening to 60F 55R. All my after market B&Cs are torqued to 65/65 and my Boyds and Sav wood stocks are 60/50. Your groups seem to have tightened up considerably at your highest torque. The more a stock flexes the more likely the screws will loosen. My guess is your groups and torque will stay more consistent with more torque than you are using now.
The action screws will easily survive 65 in/lbs and as long as they are pillared maybe you should try to tighten even more than you already have. A wood stock however without pillars and bedding might distort or even crack using the higher torque values. And of coarse with lighter torques a wood stock most likely will not stay consistent.
All my rifles are hunting rifles so I don't want them to change or "loosen" in the field. For that reason I can't imagine running the lower torque values that some of you do. But what works for some is always not the best for others.
Let us know if you run more tests.
Randy