As the header says, I'd like to know just what size is the best for doing the dual cyl. conversion. I've read the theory about large vs. small diameter tubing (I don't follow volumetric physics all that well) and the different posts. But no one has said difinitively "use this size".
The last time I did this I was in full on "get there mode" and don't remember what size I did use.

Some of you more smarter than me guys post up and tell me outright what size is the best to use.