I believe the reason for pinning the grip safety is because a lot of shooters, especially in competition, use a wide thumb safety. When they shoot, the keep their thumb on the safety, supposedly to help keep muzzle flip to a minimum.In doing so, certain hand shapes will fail to depress the grip safety, so they would pin them. I would not recommend this for a carry gun, not so much because of an AD, but for the reason Espresso stated- if you had to go to court, an improperly functioning safety would not look good.
I have a Wilson drop-in on my commander, it fit fine, but I did have to fit the part referred to by Espresso. There is a little more gap between the safety and frame than there would be with a professionally fitted beavertail, but not too bad. I agree with Espresso, if you are unsure, take it to a pro. BTW, I also have a "wedge" on my commander, and it does help.
A lot of safeties have a "bump" on the bottom, to help with the problem I described above, something to consider if you prefer a high thumb hold. Hope this helps.
[This message has been edited by lowrider (edited November 14, 1999).]