Hi David,
One nice way to create the position diagram you need is to EVERYTHING with call options from the left of your page.
Get a shouty friend and a pen and start drawing a horizontal line (left to right).
When your friend shouts "buy", start moving your pen up at 45 degrees (gradient 1).
From here, when your friend shouts "sell", start moving your pen horizontally again.
Or...
When your friend shouts "sell", start moving your pen down at 45 degrees (gradient -1).
From here, when your friend shouts "buy", start moving your pen horizontally again.
If your friend shouts "buy" when you're already going up, tell him/her to stop being a smart-arse but we can also sort this out by going from gradient 1 to gradient 2 (60 degrees, I think?).
All of this has been done with call options and the strike prices are the point where your friend shouted.
If you need to start with a slope, an upward slope of gradient 1 is sorted by buying the share, or a downward slope of gradient -1 is sorted by selling the share. BTW, a share is a call option with a strike price of K=0 (you should think about this) and so this is really your friend shouting just as you start moving your pen.
Finally, you need to get the "height" correct, which can be sorted with cash. If the final share price is less than the lowest strike of all the calls, they all expire worthless. So, if you get the "height" correct here (with the right amount of cash), all of your position diagram falls into place
Good luck!
John