Hi there beer4,
I reckon that a 50L kettle will serve you better. There's very little price difference between pot sizes and 35 L is really a bit too small.
On the burner side of things, I have a 3 ring and an Italian Spiral burner. Both are similiar in performance and easily boil double batches I do in a 70L pot. However, I had to make a stand for my three-ring to get it at the hot point of the flame and use an adjustable regulator so an Italian spiral may end up being cheaper when you consider these two things.
hashie doesn't need an adjustable regulator or stand for his 4 ring burner so that could be a better solution again! (We'll have to do some time trials

).
PP
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