Not coming all the way down to set idle

I thought I took care of this possibility when I got the carb.
Whenever I get a new or different carb I always loosen the butterfly screws and make sure they center in the carb throat all the way. (seen to many holding one open)

After getting everything all set and driving, the engine doesn't quite idle down to what is actually set at unless I lightly tap the throttle with the tow of my shoe.
I like as light a return spring as I can get that fully returns the throttle, so I thought "well I guess I'll have to use a tighter spring than I had on it".
Nope didn't do it, and actually didn't seem to make any difference at all.

The carb isn't old and/or worn really at all, but I'm still assuming it has to do with the shaft being slightly off center from the spring putting sideways pressure on it when it comes down from higher RPM and hanging a butterfly slightly, and then when I tap the pedal it centers and idles down all the way.
Nothing drastic, just about 50-75 RPM.

I have a linkage disc instead of an arm so that all the connections of the throttle, TP cable and return spring can easily be changed or adjusted for geometry so I think I may have a solution.
Being that I use a disc I should be able to use two lighter springs One from each direction to equalize the off center pull from have one spring.
I'm going to try it and see, so think it'll work?

Yea or nay? :D

linkage.jpg