Hi, name's Ken Wilson. Been flying one for 2yrs. now with the K & B 61 "Twist" head version w/pitts muffler. It is VERY fast, clocked at 120mph level with this engine. A matter of fact, it is faster than a friends GP Toni which is equipped with an OS 91 4s. I run it on 10percent OMEGA that I add 2 - 3 oz. of add'l castor (for insurance). So, IMHO, this plane will go like stink with a good 61 2s in the nose, will be lighter and will generally fly better.