when you cut the wingtip covering next time and a Sharpe single edge blade is a must i use probably three to four blades when I'm doin edge trimming is to lay the blade flat on the bottom surface as you can and slide the blade along,for me normally i get a pretty straight line still get a jag or two sometimes but for the most part they look good enough if you slightly squint............do the same thing when you cover the bottom with the razor blade as flat as you can to the surface.the airplane wont know it has slight imperfections though looks like it is built true and straight