Oh, forgot something - if you have just received this concentrator, I think it would be best to try it out before you worry about needing a tank. You may find that you don't need it and you can use the money for more glass. Plus you could save yourself from the aggravation of trying to figure out how to hook one up.
Other than my generator which is an Airsep AS-12A, I have also tried the standard 5lpm concentrator as well. It wasn't enough "juice" for my Bobcat because I was so spoiled by the generator, so I gave it away to a newbie friend to get him started. But I do remember that it had a nice steady flame. I have also used a friend's torch set-up which was a GTT Cricket and an M-15, which is an 8lpm machine. It worked wonderfully by itself with no need for a holding tank.
What torch do you have and what concentrator did you buy?