I have not painted anything yet, but I have thought about what to do with the cowl split line. My thought was to make whatever paint scheme I come up with...white in and around these hinge pin areas on the top / bottom split. My thinking is that this area will get the most abuse when removing / installing the top cowling. If it scratches during the removal process, then I believe white touch-up would be the easiest to use and try and hide my "scars".
I can easily be convinced to do something different. As I said, I have yet to paint the exterior.