I have the exact same combo and have been flying it for about 3 weeks . I didnt have to cut the cowl hardly at all. I was also worried like you but I only had to cut a small area for the plug and an area for 2 of the lowest fins on the cylinder. I also installed a 440 rod and clevis to the choke and drilled a small hole for it to exit in the lower side of the cowl. If you are not done with yours I could send you some pictures. Its not bad at all and you will have very little showing. good luck!!