The Super Sports 40S has about 1/2 an inch longer wing and it has a cowl. The Super Sports 40 has no cowl go with the 40s it looks better. I just finished mine and will be flying it tom. I put an OS 46 sf with an 11x6 prop I will let you know how it flies but since it looks very similar to my T-34 from World Models it will probably fly like it too, very straight and very manueverable.