Question about ground rule doubles

[The Max Swineberg 7]

Okay, here's the situation. The field has a fence that is 10 foot high from the left field line for about 15 feet toward left center, then the fence drops down to a 5 foot fence. And there is a sharp change in distace. LF line is 151, left center is 170. And it has angles...in other words, it still isn't a semicircle.

Batter hits the ball in the air toward left field....the ball hits the left field fence (never touches the ground), the ball shoots sideways and over the shorter left center field fence. Ball never hit the ground....just the wall and over.

Is this a ground rule double or a home run?

Any input is appreciated...and if you could cite any rules whether it be softball or even baseball, it would really help me out.

Thanks.