While that oval bladed carb looks neat and for sure flows more air, Id be concerned about fuel atomization. Looks like a whole lot of air going through without fuel contact in the middle.
I've seen 'em built with both downlegs and annular boosters. It seems to me the annulars would be better at "filling in" the middle like you mentioned.
Mark - Anyone you know done any "top down" videos of a Lil' Bo / Get'M Twin Blade that would show how the fuel coming out of the boosters transitions into the "big hole" below 'em?
