You're welcome. I'm sorry to say, but the Major/Minor is probably a bad choice, if running on concentrators is your goal. The major is a lot of torch for the money, but it's not very efficient with oxygen - some say that other torches can do about twice as much work with the same oxygen supply.
To power the Major enough to not melt its own face off, I think you'd need somewhere between 3 and 6 EX-15's, and probably around 9 to 12 of them to fully power it.
If you can, the easiest option is to just use tanks for the Major part of the Major/Minor. I'd still add a second concentrator so that you can get the most out of the Minor, then only use the Major when you really have to. If this works for you, you can get a Homefill machine to fill tanks for you overnight, but those tend to need frequent fixing.
If you can get liquid oxygen, you could just run both fires off of that and not worry about oxygen use ever again, just fill your tank when you need it.
If you have access to somebody handy, a DIY HVLP oxygen system might serve the same purpose. Or, if you have money, you can buy a pre-made set-up from OxygenFrog or HVO.
If you can use natural gas instead of propane, that'll help cut back on your oxygen use a little bit.
Basically, you can either get tanks/liquid and spend money and deal with the supplier every time your tank is empty, or sit down and do a lot of research to really understand your other options. Lots of info on HVLP systems and Homefills over at talkglass.com. Running a Major directly off of concentrators is really not something that people do.
If you're set on running directly off of concentrators and not using tanks, HVLP, or homefill, then you should consider a different torch - probably a Bethlehem Bravo, GTT Sidewinder, GTT Scorpion, Carlisle Hellcat, Knight Bullet - basically any torch with two stages and somewhere between 12 and 21 ports - but you could go ahead and get your (3+) concentrators ready and try the Major on them, just to make sure it isn't going to work out.
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