never footbraked, does the master cylinder size/piston diameter make a difference in holding the car back, hence more starting line rpm?

Yes, the smaller the bore MC the more pressure but the longer the stroke as it moves less fluid. The larger the bore the less pressure but more fluid moved. Size of caliper or wheel cylinder pistons matter also and have to work with the MC sizing. At the caliper wheel cylinder end the larger the piston the more pressure but it requires more fluid volume.

He pretty much covered it. You can get more pressure if you need it for a larger MC bore by changing the pedal ratio also. Most times you just don't have room to make large ratio changes though.

ok thanks guys, I just didnt know it was common practice to experiment with MC's, or just mash the pedal for all its worth!

I would think if you called the brake manufacturer of your choice they could figure the area of the brakes you want to use and give you a recommendation for master cylinder and pedal ratio.

How did you turn out? Another tip too is to select brake pads and shoes with good "cold bite".
And maybe drag your brakes in the staging lanes, to warm them a bit.