Off the topic a bit as I know there is a Bob Cat forum not to be confused with the later use of the name by my hero B.V., that being said I had several and found the light weight 9.6 Oz HP 40Silver Star really was the engine for the "Tiger tail JR IE Bob Cat any one ever install the HP40 in the Southern R/C Prod. Bob Cat back in the seventies mine was a beaut with more performance than I knew what to do with back then So one day I was slow flying it (it was HEAVILY finished in the old K&B polyester resin and weighed a ton)and spun in to the pits lucky every one that day