Hey, we were all in your position at one time.
Your idea seems like it would work to keep the smell in, and if not, you can one of those glass mason jars. If you don't have one just lying around, go into your pantry and look around, you're likely to find some type of jar that would work. Rinse it out and give it a shot.
You don't want to use PVC, plastic vapors are HORRIBLE for you. I don't think 1/8 inch is too small, it should work fine. Try just sucking through it without smoke, if it seems like its too small, then get a bigger size. This isn't an exact science, experiment! .
And finally, the opening in the brass pipe is fine, the only thing that may happen is that it may get hot, but thats the risk you take with metal parts. I smoked out of a metal piece that had about a one inch plastic(A clear plastic tubing) around the mouthpiece. It was snug, but I'm not sure how that was done. If the hot metal gets to be a problem, you might want to look into that.

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