If someone is looking to do an upgrade just do it right with 240V, 30A branch. An outlet like this is good for 5.76KW continual and ebay has tons of cheap used PDUs which have a NEMA L6-30 plug.
This is extremely good advice. I did this, and I now run all 9 of my BFL singles on the PDU (only 9A at 220V). It only cost about $300 for electricians to do the run.