The A1 top screw is exactluy the same as the A2 screw but is shorter by 5/8 ths of an inch.
From the maryland website:
Q: How do I change from the A2 to A1 Stock?
A: Read the -23 for the detailed instructions. But its pretty simple. Remove the upper screw from the stock. Removed the stock & spacer. Slide on the A1 stock and use the shorter (by 5/8") A1 upper screw. If you can't get an A1 upper screw - then cut your A2 upper screw 5/8" shorter.