A plumb line is your friend here guys. Use it to calibrate an anti-cant level mounted on the scope.
The Reticle-Tru helps minimize scope cant relative to the centerline of the bore, basically. That's nice and all but it's not really the solution to the problem of shooting canted. You can still cant the whole system.
An anti-cant level on the scope (or mounts) CALIBRATED to a hanging plumb line is what solves this issue. A real, hanging plumb line works better than drawing a line on a target with a level.
