Sig Cross
Mill off the front lower section of the stock to mount the ABR to the existing lower section of the stock. Mill clearance to the LOP plate to clear the rear dowel. Alter the existing mounting holes in the Flat Mount ABR to match the existing ones in the stock. Drawings are available to assist proper installation. Flat Mount ABR with short dowels in pic.
The Rules for adding an ABR
Do not raise the rear stock more than absolutely necessary
Space behind the grip to the front of the ABR minimum is 2+” so the adjustment hand is not hit during recoil
ABR parallel with the bore