my gsxr setup is designed for the 88-02 cable brake blasters with the floating disc,
the gsxr caliper is mounted solid, just as it was on the gsxr it came from.
the 03+ hydro brake blasters, have a solid disc and floating caliper.
i don't see both floating as a problem,
but one or the other has to "float" to promote even pad wear.
except........ a dual opposing piston caliper,
like the gsxr's i use.
it can be solid mounted on a solid mounted disc, such as a banshee axle equipped blaster, and still produce even pad wear as each piston pushes it's respective brake pad independently of the other.
even if mounted slightly off center of the disc, it will still push both pads the needed amount to apply the same pressure to the disc = even pad wear.
on another note, i have seen quite a few "floating" calipers freeze up (pin sliding in rubber + dirt/grime = locked up)
but have never seen a floating blaster disc seized to the axle
not sure that answers your questions, but thats what i've experienced in my quest for the best brakes ever put on a blaster