[QUOTE
In the event of a failure in one part of a dual system, the pedal will typically have to be pushed
a long ways down before any breaking pressure is created in the other part of the system. If your custom application does not have enough pedal travel available to reach this point you will effectively have no braking pressure in either part of the system. A smaller cylinder diameter will increase the amount of pedal travel and increase the likelihood of this happening.
Dual systems are not near as fail-proof as most people assume.[/QUOTE]
For my installation, I needed more travel to provide feel and modulation; the smaller cylinder MC solved the problem.
If the MC is working properly, a leak in one circuit will not prevent the second circuit from safely applying brakes.
Please review this file for an explanation of the operation of a dual reservoir MC:
https://shop.wilwood.com/blogs/news/...he-rear-brakes