I would think that the need for the larger jetting would be from a decrease in velocity through the intake track due to the increase in reed area. I was waiting to see what jetting changes would be needed and I'm not really shocked by the findings.
Obviously, people going from a stock reed setup will see gains. What other reed setups were tested and on what type of motors? Reason I ask, is that Majority of the people buying these will have near stock motors. Previous dyno testing has shown that these stockish motors can't generate enough draw through the intake to take advantage of the VF2's and VF3's vs other setups. (not saying they performed bad) As the builds get bigger.. the VF cages start to pull away. My stock cylinders have the option to use CR125 cages.. But I was told by a couple builders that I wouldn't see gains. Which is probably why the big reed conversions died out, except on the big 465+cc engines. If more is better.. why are the top builders that are setting records not using big reed conversions on their smaller motors when they clearly have the means?
Not hating on the VF4's.. I think they have their place.. Just like I think the older VF's had their place.
JMO of course..