Hi Jim
The stroke will stay to same .I've changed bikes over to dual calipers where you have 4 pistons afterwards instead of 2 on one side . Never have to change the master or have to even adjust it.
Remember your still moving the pistons the same amount of travel.
Just like an electric light switch you can turn on one bulb or 100 all will stay the same with the switch(yes if the is enough amperage to push that many bulbs and the switch can handle the load)
As I said you could run 50 calipers the stroke would stay the same .
Paul


1948 Chevy 2 ton flatbed ex fire truck , and various motorcycles .