NOTES:

Here is a view of the heater wires. Each tube has the heaters on pins 4 and 5, and all three must be paralleled together. Don't let the appearance of three wires confuse you, I simply connected pin 4 on the left socket to pin 4 on the right socket and then came back on the same twist and ended at pin 4 on the bottom socket. Then did the opposite for pin 5. As you can see this keeps a clean layout.