Just like any lipo your pack is only as good as it's weakest cell. I have seen a couple guys run completely different packs with no problems at all. I myself have never tried it. The only issue would be run time. You wouldn't want to run your 7200 lower to where it would effect the 5400. Best way I guess is run it for a few minutes and check battery on the charger to see how much mah it used.