I'd be careful about how much you file off for starters. That center pin is the electrical connection between the battery and the head. Take off just a little to much and no connection and the head is useless. If you wanted to take any off you could use sandpaper but that will be kind of slow. A file or emery board would work much better, but again, be very careful not to overdo things. The easiest way would be a high speed grinder like a Dremel but that would be very fast and therefor harder to control.
I think the misfires or nonfires I've had are more a result of corrosion/dirt interrupting the connection between the shell, socket, of the battery and the head. I usually clean the seat area and the head with an alcohol swab when that happens and everything works fine again, until the next time. It doesn't happen all that often, but it does happen sometimes. I notice the plating down in the bottom of the socket isn't as good as the sidewalls and I think that's the real cause.
Just my opinion, worth what you're paying for it. Your results and mileage may vary. No warranty or guaranty is expressed or implied.