Engine Cowls

I have a Golberg Anniversary Cub and am replacing the flimsy original ABS cowl with a fibreglass version. I had to cut the rear of the old one (to the rear of the engine) to get the cowl over an OS46 FX mounted horizontally with a pitts style muffler. I'd like to maintain scale as much as possible. I have seen methods where the entire area behind the engine has been removed but it doesn't look right. How was the cowl on the full size J3 attached? I have seen another method where the top and bottom of the cowl were separated and then screwed together. This looked like a better approach but the cut had to be very precise and looked tricky. Any assistance would be much appreciated.