Beyond that - don't mix the A721 and A741 on same controller.
They run fine but -- when upgrading the miner Firmware it is applied to all miners on the controller.
There are specific versions for the 721 and 741 and neither likes being flashed with the wrong version... Been there, done that....
Thanks for the heads up! I guess luckily they sold out of the 741s before they could get me a BTC address, so I didn't run into this. I hope they get you your fan, though! (Also following the A7 thread.)