Showdown devices seem to work okay if you're playing with no superweapons. Superweapons make the Showdown response scale up far more than the Superweapons are giving you, making it a negative to attempt it.
FS is the worst for that, and if you're far enough to build the transceiver you should really just do that and ignore the Showdown devices. As you saw here, the Showdown response is absurd.