You know. Your question just made me think of something. Are all 4 of your bec's powered going to your FCB? Only 1 should be powered. I am not a electronics expert but my experience with high end audio has taught me that wires run in parallel close together create quite a field. It has a very dramatic effect on sound quality. I am not sure that this is what's happening to you but I can't believe there would be no interference. Especially from cheap esc's. Anyway. The KDE and ZTW esc's are opto. They have no power, just a signal going thru the bec lead. A ubec gets its power from the battery input of your PDB then drops the voltage to power your FCB which powers your Rx. Both the Castle and KDE ubec's can handle sufficient amperage to power other devices, servos for example, with no problem.