Hi Moerig,
For those of us who don't speak geek (

) are you talking about the SBus lead that connects the RX to the Powerbox or something else? PowerBox supply 20cm leads with their SRS units and state that if you want longer you can "make them up to 1m but don't go longer than 1m" - is this for the same reason you state?
Rgds,
Mark