So the problem here is matching the color on the plane. That problem will remain whether the cowl is fixed or not. And if you build a fixed cowl, you are virtually eliminating the option of painting the cowl to match the plane. Since there is no break line between fuselage and cowl, you are pretty much limited to covering the cowl with the same stuff that you are using on the fuselage. If you build a cowl that is a totally separate piece, you can take a small piece of covering to your local automotive paint store and they can match the color perfectly and put it in a rattle can for you. You then fill the balsa with your favorite filler, sand it smooth, and paint it. It will match perfectly. You then have the added advantage of being able to remove the cowl if you need to do something to the engine. And getting to those screws mentioned in the first post becomes no problem at all.