5c lipo battery help

[hobbimaster]

Here's a question someone might have already tried. If I already have a 3C lipo (11.1v) 4000Mah, and I want to try running 5C can I simply purchase another 2C 4000Mah (7.4v) and wire it in series with the 3C to get the 5C total voltage, will this work? Right now I have a MGM 16018 and run 2-orion 4800 lipos in a series harness. Is it absolutely necessary that the Mah match, Lets say I wanted to run the 3C 4000Mah, with the 2C orion 4800mah. Would the lipo cut off cut the packs out before the 4000mah pack get too low?