It's really a piece of cake. The #2a is nothing more than a small, curved plate with a threaded sleeve installed in it.
If you look at the inletting of a wood M14 stock, you'll see a small "well" carved into the area around the weep hole. All I did was grind away the corners of my #2a mount until the plate fit directly into the well. Then all you do is mount the Harris bipod from below using the weephole as the entrance for the thumb screw. It mounts in seconds. It also dismounts quickly, too.
I tried the M2 version. I was extremely disappointed with the alteration to the POI on my targets with it. The rifle shot all over the place. Maybe it worked fine for full-auto, but for accurate shots, stay away from any bipod that clamps onto the gas system or barrel. In addition, this is already a heavy rifle. The aluminum bipods are extremely light.
There is another brand of bipod you can also purchase with is virtually identical to the Harris bipod. These bipods are made by Shooter's Ridge, distributed by Outers. From what I've read, the patent on the Harris design expired and Shooter's Ridge/Outers copied them virtually verbatim. They are even sold with the same dimensions. I mounted the 9"-13" version. I have one and a Harris and I can not tell the difference, truthfully. Both the Harris and Shooter's Ridge use the same Harris #2a mounting plate.
My Polytech shoots sub-moa groups with it on. I even had a expert marksman soldier try it and he agreed that it was a tack driver and the bipod was identical to what he'd seen.
Rome