My capacitors are sometimes backwards. Sometimes upside down. I'm trying to figure out how to get them to be inside out. It might be a while on that one. Go ahead and test for outside foil if you want to, I'm not interested in it. Every 4 and 5 gain stage Hi Gain build I've done has worked/sounded just fine without sweating Outside Foil Orientation. I put this in the "Run, Forrest" category.