[x5_Potter]

I haven't played but looking at the pictures I feel the natural is the wrong side of the ramp. Looking at most maps the ramp flows down straight in to the natural base but in yours you have to sort of move around the corner first.

I think by expanding the natural outwards at the bushes in the corner and placing the minerals there, you could cut down the size of the extra little bit on the main to enlarge the ramp to the third.

I also think the position of the third would make it really hard to defend, as the distance between natural minerals and ramp to natural for the enemy is huge, and units could easily sneak through unseen if needed.