I would not advise mixing 2cb and methamphetamine for a number of reasons. For starters, RC's are pretty unknown chemicals and using them on their own is enough of a gamble without combining them with other drugs. Furthermore, it is not really wise to use stimulants with psychedelics as stimulants often make people prone to paranoia.
It is possible to combine these drugs without incident but not really worth the risk, plus you are guaranteed a pretty shitty comedown.