Eddie, yes we do coat the fuel tank top sides with polybrush before covering. Then when brushing the first polybrush layer on the new fabric, the mek based polybrush will re-soften the polybrush applied to the tank tops and meld them together. If you have ever tried peeling a properly applied poly fabric from a surface that large, you learned quickly how effective the polyfiber system really is. It is almost permanent unless you re-activate the polybrush with mek before attempting to remove fabric fom an airframe. Following the Polyfiber manual and the recommendations in your Kitfox build manual will give you real peice of mind that your aircraft's fabric will have a 20 year plus useful life.