That was just the answer to your question. You can have a gap on the Edcor as well. You just need to find the practical solution which means enough inductance together with enough headroom in case of DC unbalance. You can start trying with 0.05-0.1 mm.
In your case you also have 8 power tubes to play with and I am pretty sure that if they measure within 10% one from any other for current and mutual conductance it will be easy and straightforward to make pairs so that you can find dynamic balance with little adjustment together with good DC balance using a single bias network for each pair.
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And thanks for your answer. The tube cost alone is gonna hurt. I think your right about the tubes.
Athos