btw jkmakowka brings for a very important note, alphatested stuff will not work with stencil shadows anyway, as volume extraction is done on poly basis, not pixel.
There is no point in leaving no space...you should always leave some pixels spacing...the point of leaving as little space as possible is maximizing the texel density.
Editing the normal map in Photoshop, but only because I don't rely on the bake for everything. It's just a small area worth of pixels anyway, and not that complex.