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One question: what torque should I apply to the bolts that hold the forend together and hold it onto the backbone?
Thank you for your post, that says good things about your character. We've all done something similar but not everyone owns up to it.
Regarding the screws for the forend, 20 in-lbs should do. I go a little higher on the ones that go into the aluminum backbone. When you do put those screws in, it helps to tilt the forend down as much as possible so that the tip of the forend is further away from the barrel and that will help with the flex.
I sent you a PM about another thing.
Thank you for your business.
Justin