[Arran]

 Here's a tip, save the 6E5 for something else plug a 1629 tube in there, it's the same pinout as a 6X6 but with one shadow. Yes it's got a 12.6 volt heater but on a strong testing tube it will still work, and it will probably live longer at near half the voltage. I have a Deforest Crosley Elgar that someone butchered to put a 6U5/6G5 socket in it, and mickey moused a 5Y4 rectifier in it, eventually it's getting swapped back to using an octal eye tube socket salvaged from another Rogers product, and a proper adapter for the rectifier. I don't even know where you would find a NOS 6X6 tube, but I can't imagine that many people would pay $90 for one just to have the novelty of a dual shadow eye tube.
Regards
Arran