Oh boy, now that we know your interested in scale accuracy, I have some bad news for you. Your plane is not scale correct and never will be. Don't let that bother you, just make it look as "right" as you can and enjoy it. In my Cub collection I have five J-3 ARF's and none of them are the same. They all look like J-3's but all have different side profiles, different wing cord to span ratios, different tail feather shapes and sizes, and different cowl shapes. All the cowls taper to a correct narrow front except a World models 48" electric cub that is shaped similar to yours. Electric motors need cooling too and I cut two cheek openings on either side if the spinner and declared it to be a "super Cub"! As John points out on your Cub cowl, it's too wide to be a correct J-3 cowl so maybe his idea to cut cheek openings is a good one. I think there is enough room on each side to make two openings that will sorta look like a PA-18 and I would still open the oil cooler bump that's on the bottom of your cowl. With the incorrect too wide shape not enough of the engine sticks out in the air stream for cooling and cheek openings would help fix that. It still won't have the correct PA-18 shape viewed from the side but your going to have to accept a compromise. Fact is most flying scale model airplanes have been reconfigured for better flight qualities once they are scaled down from full size. This applys to kits as well as ARF's. Tail feathers get made bigger, fuselages get lengthened, etc. Contest quality models don't have these changes but the ones us "sport" flyers have do. Generally speaking, the higher quality brand name kits and ARF's will do a better job of hiding any inaccuracies. Lower cost "no name" ARF's will have more inaccuracies and and will be more visible. That's just the way is. The more scale details you add to these types of planes the more convincing it becomes. In truth these are "semi scale" planes, some more "semi" than others. Your stuck with that cowl, make look as convincing as you can. Some of the major visual differences between a J-3 Cub and a Super Cub are: most but not all Super Cubs were built with flaps, the vert. stab/rudder shape is a little different, and the enclosed cowl. For $85 just style the cowl openings like a Super Cub, call it a Super Cub and enjoy it. As you know, modeling is all about creating an allusion. Fake it!!