I know 4 is stable, but "that is all I see" doesn't really answer my question....
I was an engineering grad student as a young man so the question was largely rhetorical. I just get a little disappointed at some of the stuff folks come up with. I don't know all there is to know; in fact I would defer to many of you often. In fact, I've recently asked for expertise in these forums. However, I get discouraged at all the unqualified answering going on here. Why don't more guys think to themselves "I don't really know.", and realizing this, find out or not respond. That way we could honestly get good info. To illustrate my point, just this morning I offered to purchase props and a pipe so another member could thoroughly conduct a comparison between 30cc engines which he already owns or has on order. I hope he accepts my offer. I did this because I have been reading posts for days about which one is better and noone has actually compiled any data to support pages and pages of speculation. My brain getting tired, I decided it would be best to just shut my mouth and open up my wallet in an effort to help us all find out.