place the cowl on the fuselage where you want it, don't fasten it to the plane yet. take a measurment from the firewall to the outside of the cowl through the hole where the crankshaft sticks out. add whatever gap you want for spinner clearance. mount the spinner backplate to the engine. set the engine in the engine mount and measure the same distance from the firewall to the spinner backplate and mark and mount the engine. this will be close and you can make final adjustments before you permanently attach the cowling. i hope this helps and good luck flying your edge. I have had students that are ready for this type aircraft as their second plane too! I think the others are just jealous!