Cylinder volume of hydraulic brakes and levers I've been asking around for a while now but even workshop pros couldn't answer this (by citing exact figures):

How big are the brake cylinders of disk and rim brakes in terms of volume and surface area? Specifically the Shimano RS505/685, SRAM Force and Magura HS33 R (FIRM-tech).



EDIT   I intended to build a full custom solution working around some of the limitations given by the brake manufacturers.

In short, shifters from brand A on brakes of brand B. I went a different path so I'm not limited by this question any more.
Is it not a sealed system though? 

If the reservoir holds 30ml fluid the only difference will be the fluid within the brake lines adding to the total capacity of fluid needed or used.

Even when pads get low you don't lose fluid, it may seem like you have as the reservoir will look like its gone down, it has but you still have the same amount of fluid you started with.