I got ya, and I'm not trying to come across as rude or anything. But really you have 3 simple options and its just doing one of them.
1) don't use the reg, but you really want to
2) grin/file down the pin, this is permanent to the valve
3) notch the rail, if its stock there are plenty out there to buy for cheap, if its a nice 1/10-20-30 rail then I can see how you'd be hesitant to at least just trying it.
But you're gonna have to pick one of those
Let us know how it goes