John

I built and flew an Utter Kaos in the SPA using an Evolution 60NX. The 60NX is a smaller case 60 similiar in size to a 46 or OS 55. I had real good luck with the engine and it pulled the Kaos unlimited. The weight of the Utter is 5.5lbs and is similiar in design to the Killer except the Killer has the engine side mounted.

The Evolution 60nx runs well with the stock muffler and really screams with a Tower Hobbies 46 muffler or a Evolution tuned muffler.

I was not tail heavy for my flying. Although I did cut some holes out of the rudder balsa prior to covering to offset the lighter weight 60.