Im not sure if this is what you are asking, but -
For filling the reactor with veg, i doubt that flow is that important? If it takes 1,3,5 mins longer or shorter, is that worth thinking too much about?
If you are talking about filling through the venturi, as in through the sucking port - i know people do, but id much rather use a pump to pump or suck the feedstock in. Besides, i find the venturi gets blocked if im not carefull.
As i say, im not sure if that is relevant to what you are asking or not!