Back coating creates a cylindrical tunnel, coupled with high shear printing will give a greater fluid pressure head leading to a crisp dot. Coating substrate side will create a funnel, not a tunnel, and the resulting pressure and thicker gasket will result in increased dot gain. I'll try to dig up some slides later to illustrate what I'm talking about.
Slides of stencils? Sounds like fun to me.
To clarify, I agree thickening the stencil is poor practice, I was just mentioning that a stencil with a poor Rz on the substrate side will suffer from dot gain, especially printing it on top of flashed ink, and that a face coat on the substrate side is likely to improve that without significantly increasing stencil thickness.
