Any question answered...

Borderline in what way?

The tyre won't work quite how the manufacturer intended. You could run off the edge of the tread, or find that the tyre steers like a triangular Dunlop. You could get funny handling due to too much or too little sidewall stiffness. You'll probably want to avoid extreme pressure setting at either end of the scale. You're more likely to find that you can't find a pressure which gives good ride and good handling. The tyre might be more likely to come off the rim when punctured. That sort of stuff.