I don't have a problem with ordering things online. Just use a credit card, not a debit card. (If at all possible.) It's nice to have the big CC company on your side if anything goes wrong.
I presume you're trying to save time by cutting all the layers together, but I'm not sure it's worthwhile...
Superglue? Or just solder/braze them together.
Maybe I'm missing some subtle issue, but with the right mandrels, which everyone else is mentioning anyway, wouldn't you be able to use a standard tube cutter? Just slide a scrap piece down the mandrel to rest against the piece you want to cut, and it will be supported on both sides. You would...
Or the Sea Dragon. It's one of my favorite rocket concepts. It was designed to use 8mm steel sheeting, which would give it a really high dry mass, but the 23m diameter and the square-cube law come into save the day. It's got ridiculous lifting capacity (550Mg) and was totally feasible with...
They sure aren't wasting any time. This means they've probably got a good idea what went wrong with the tank pressure and that they can fix it with minor adjustments on the pad. Perhaps even in software.
Or they need more room to stack new rockets. Maybe both...