Rather than turn off the powerflarm core, simply turn off the FlarmView that is connected to the Flarm. Intercepting the power lead in the cable going to the Flarmview and routing that to a panel mounted switch will keep the Flarm running (good for your flight log and keeps you visible to other Flarm traffic) and you won’t get annoying beeping while on tow. Once off tow, you can power up the Flameview and be on your way.