John, I consider mine to be an on-off valve. In chemical engineering land it would technically be a pinch valve and could be used proportionally. However the shape of the parts is such that proportional use would not be very workable. You probably want all the smoke you can get anyhow.
Chuck

Thanks Chuck,
That is what I thought also.  I hope to bench test the setup this weekend.  If I get too much oil flow I will add a pinch valve. I have an article that shows how to make one form a block of wood and a 1/4 - 20 nylon screw.  If it all works I will post details.

Well I have smoke!  It appears that the Dubro Super Smoker is a good match for my ST G90.  This is my first try at smoke so I don't know how much is enough.  But to me it looked like I got enough white smoke to be visible. It looks like the on off action is all I will need.  The system uses crank case pressure to pump the oil and it looks like wide open the flow rate will be just about right. I did learn that It will require full throttle when I want smoke.  But that is OK because I want smoke for loops, wing-overs etc. these maneuvers will be performed wide open so all is good.