I'm now the owner of a low time 1.20 twin.
I will experiment to see if I can get it to run reliably. If I have an paticular finding that may be of use, I will post again on this thread.
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Here is a link to a video showing a twin which appears to run well. Inpiration for the rest of us.
http://www.youtube.com/watch?v=LlLyHpLAKqI