I'm a big fan of using a thumb activated tailswitch (see above) over a pressure switch, especially on a 12 gauge. Pressure switches, even high end ones, tend to fail....
As to the VFG, be careful about that one. Running a VFG on a pump can
unevenly torque the receiver and damage it eventually (see www.aipitactical.com
for a better explaination/examples).