What accessories are you mounting to the handguard that are used for aiming and why aren't they on the top rail?
I've never seen that rail before. My bad. I'd immediately want to mount a dbal in the front. Assuming it's this one:
I would have assumed those socket head cap screws were going into the ACR receiver's threaded holes and not the QD notches.
Yup, precision drill holes in the HG so it's a more permanent fit. Maybe beef up the pegs that go in the notch so they are a tighter fit as well.