What you are saying suggests that there's a single number (that can be positive or negative) that characterises your net short or long position.
That's silly.
You can build pretty much any kind of shareprice-to-payoff function with enough options and other instruments. And that's one dimension (a line) more than just a single number. You can get arbitrarily more complicated, if you want to.
You may hold a short position as part of a net neutral or net long position with extreme caution.