Quests for parts sometimes turn into life long endeavor: Glad you found your forks.
Now I need to figure out where in the hell I have packed these calipers
Once I find them, I would be happy to measure the pistons.
Out of curiosity, are you going to calculate the volume of brake fluid? For those of us without a proclivity for math, it seems simple to go with whatever MC size was used on the donor bike. For instance the ZRX1200 came stock with these 6 pots