Forge questions

[WNC Goater]

Okay, I'm trying an experiment. Building a small forge from a fire extinguisher and have a few questions:

1. I know the burner needs to enter at a slight angle to cause the flame to encircle or swirl around the chamber, like at 11 or 1:00. But longitudinally, should the burner be installed at the mid point of the chamber or slightly forward of center? I could see if it were too far toward the back a longer blade may not be able to be heated evenly toward the tang end.

2. Any good ideas on how to drill the hole in the side and enlarge it as necessary for the burner? Grinding stone in a drill?

3. Necessary to coat the koa wool with refractory cement? I assume to keep the wool fibers from getting airborne and to keep from snagging it?

4. Single or double layer of the Koa wool?

5. Do I need a hole in the back for any purpose other than extending a longer blade's point through? Does it serve any practical function otherwise, such as allowing the flame to more evenly heat the whole chamber?