Steve,

Required diameter for .15 to .40 engines is .015 for stranded wire. Length for the .25 in a Super Clown should be about 60'. Line size .015x60' is a standard length.

George

Edit: Forgot to answer the other parts. You will need about 3 to 3 1/2 ounces. I would go for the 3 1/2 to make sure. You can always put in less fuel. Brodak has them. Check the one they recommend with the kit (Brodak always suggests whatever you need to complete the airplane).
A uniflow is plumbed to keep an almost even pressure on the fuel feed from start to finish so your needle valve setting stays constant throughout the flight.