Hi Ivan, my name is Roelof. I lived in Portugal for 15 years where I built two batch rocket stoves, suitable for a warmer climate like Portugal's. Also I instructed a builders group to make another two. Two years ago I started a website about it (roquetinho.eu), and just this week I uploaded an improved version of it. It's a simple step-by-step building plan, together with Sketchup 3D files.
I hope this can help you. I live in Holland now, since I lost everything in Portugal in the wildfires of 2017. But I'd be willing to support online.
I believe that builders group is still active, so you could try that too. They are located around Tabua / Oliveira do Hospital and their website is batchrocket.pt.
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