Well I've been told this plane is very tail heavy, so if I'm going to have to add weight to the nose it may as well be useful weight, and yes I want plenty of power on tap for 3D flight.
I have an original Hangar 9 Funtana 40 with a Saito 82, it came in at 5 pounds 5 ounces, the Saito does a great job hauling the Funtana around, but I've always wished it had just a tiny bit more power, so I can't imagine that motor doing very well with a 6 plus pound Katana, if I was dead set on running a 4 stroke I would go with a Saito 100 or the new YS fz80