Thanks Peter for the response and clarification! I'm in the process of building a batch box core after succesfuly building a j-tube one. I'm very interested in the performance of it and I'll certainly post some video's of it burning on my youtube channel "Rocket Stove Experiments".
The reason I asked is I can't stop thinking why commercial boiiler manufacturers don't incorporate the rocket stove burner cores in their appliances...
After tinkering a lot with a j-tube, I'm turning my attention to the batch box core, as I think it is a far more practical thing. The j-tube works fine, but needs constant tinkering, so I'm gonna build a batch box following your dimensions and I'll have a look on how it performs...
I'l keep you posted
(PS: although I know you and me speak the same language (dutch), I want to keep all conversation here in English, as this is a very international forum off course)