RE: Why would you "build" a kit rather than assemble and ARF
Building an airplane like an ultra sport or a kaos or something that is simply a classic airplane is just like flying it. It's like the scene in "Days of Thunder" where Robert Duval is talking to the tube chassis of the car and describing what the build process will be and how it will benefit the car. That's how building an airplane is for me; especially an airplane with classic traits and qualities like an ultra sport.
I too have a US60 with an OS 61 on it with a macs muffler, I know what you're talking about exactly. Unfortuantely mine has suffered from a somewhat more than minor crunch due to a dead stick (was having so much fun I ran out of gas). Once I finish my Kougar I'll be working on the repairs and might upgrade the engine to a 91 4 stroke.
The last 2 or 3 years myself I've been building a bunch of ARFs and I'm just not satisfied with them. The build process is usually just annoying where as when I build something I'm able to follow the directions and if I don't care for it I've got bare wood and my mind to re engineer it. I'm to the point now where I simply am burnt out on ARFs and while there are some that I like out there - I just don't seem to have much interest in them.