I've read some articles & posts that hinted "Don't ever drain the master cylinder or you'll be sorry!"
Is it any more problem than draining and fully bleeding a conventional master cylinder?
how should it be done, if it's different ?
I'm considering to do it because the car has been parked 10 years and I'm planning a fair amount of overall brake system disassembly (larger rear brake cyls, new pressure switch & accumulator, new combination valve, braided teflon hoses, line lock, etc).
So I'm thinking to drain as much fluid as possible from a low point (to reduce any potential messes) , and to refill with 100% fresh new fluid.