[CircuitJerk]

If I were going to cut anything, it would be some other black material to cover the dead pedal entirely. Could even fab something up to make it look cool.
Heck, find a nice looking dead pedal add some more rubberized material behind it and rivet it to the mat. You could even fashion a clip to snap into the holes on the original dead pedal.

Cutting that part out pretty much destroys it's effectiveness. Especially if you have a little lake going and you hit the brakes.
Standard all weather mats don't cover that area. You'd get a lot more seepage behind the mat if you regularly rest your foot on the dead pedal.

What's even more fun is trying to get the mat out without spilling it all over anyway..LOL