But how about tying the two boards together? I'm (over)thinking ahead to when you have two boards and two power supplies, with two ground points and then where do you tie the ground for volume and output ground.
If I were to make a two channel, fully integrated EHHA similar to the SOHA II I would definitely build in an e12 just to be absolutely safe. But, we may not need to do that here.
A two channel board with integrated power/heater supply would rock for building. And then two boards would equal a fully balanced rig.
Maybe it would be dreaming, but then having the two channel board fit into a 1455T2201 for total ease of casework...