[PbFut]

Why would you need same size reservoir on each circuit? It is a fluid reserve to take up space in the caliper as the pad wares down. It is not likely the caliper piston is same size front to rear. The master piston should be correctly sized. Reservoir is not reletive to caliper performance. Each circuit relative to the calipers is sized to provide the correct volume of fluid to proportionally provide the needed pressure of the piston against the pad.