Home run or not???

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Temp fence. Ball to outfield, OF goes back, steps on fence enough to tilt the fence out about a foot. Ball come down on top of now tilted fence and bounces over fence.

OF did not touch ball. Is this a home run or a ground rule double?

The logic used was that the OF caused the fence to be tilted thus it's a ground rule double. That's what was ruled. Didn't make sense to me at the time but wasn't my call in final decision.

I'm say home run because the top of the fence was even further back from normal and if ball hit the top of the tilted fence it would have been out of the park with a non tilted fence.

What say you?