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Yes but mortals are so easily addicted your time lust would spiral out of control forever craving more and more time, culminating in your body reverting back into a genetic soup of sorts. Not pretty ;)
I know some people at Allegorithmic, I can try to track someone down there for you to talk with if you need :)
If you do that in the inspector it works but that doesn't enable you to utilize the power of Substances, which is real time altering of the texture using code to drive the various parameters you have exposed on the material because you aren't using the material.

If you try to select a Substance image in Shader Forge for a Texture 2D, Unity crashes to desktop. Reported: Here

Also, if you switch the shader on a substance material to a Shader Forge shader, it causes your generated images to be deleted. Reported: Here
I agree that we need substance designer material support, the best shader system should work with the best material system after all.  Personally I have been using Substance Designer for years and have setup a lot of stuff that I cannot use now that I switched my shaders to Shader Forge.  
I would if I could but the character I need it for is a jellyfish, not a leaf ;)

So is the alpha sorting an issue with Shader Forge?
Is it something I can so something about?

Thanks for the quick replies BTW :) I have made more progress with the shader.
Awesome, that worked but I do also need an alpha blended version of the shader so... how would I go about getting it to work properly while alpha blended?
I picked up SF and found out how to do some of the stuff here so I guess go ahead and close this and I will jump into the Unity forum for future questions.