I know that a few of you have tried this, and I will probably spend almost what I can buy an Eko 25 for minus the tax break buttttttt what fun would that be? I am looking for some guidance on nozzle sizing and firetube surface area. For an eko 25 size or similar I was thinking 8 or 9 2 inch id. tubes 40 inches long for firetubes The nozzle is a bit harder to tell from photos, maybe 1 x 8 inches? I have a good grasp on the theory and basic design, need to control primary and secondary air and so forth. What I need are few of the more critical dimensions. Would save a bit of cut & try. I do have a folder on my laptop with Nofo"s brothers pics of his boiler and they have given me many good ideas, Have studied them for a while now. :coolgrin: If any of you eko, tarm or econoburn owners happen to know some of the dimensions or even approximately, close or maybe that is more than what I have now.