I dont know the specific foil, but was it to be understood as the front wing was mounted correctly, but the stab upside down because the fuselage was?
If so, it might give a very odd trim, and be nervous like if stabless (a rodeo horse maybe), but you should be able to ride upwind, standing a lot further rear than usually, especially if you ride strapless
Very difficult to ride, but if one can manage, upwind will work even if stab is upside down.
You could go even higher upwind and in less wind, IF you can ride steady, as the stab lifts now.
But in reality this is not possible, so everything feels wrong, yes
If both wings upside down, it would not really work, no.