Cap'n,
I don't know about others, but I'm struggling with all the different potential engine configurations? Radial, flat, inline, V? When you speak of 3 and 5cyl., you're narrowing the comparison to radial and inline, and then trying to compare how smooth those are compared to a 4? The inline 4 isn't the smoothest (especially compared to a tripple), but geez, make it flat, and I think Goldwing, where it's hard to tell it's running?

Bottom line, I think I'm missing your point?
-Al