I ahve only a few things to add, but they may be helpful.
On the idle restrictor, the difference between .031 and .034 is pretty big.
That's a starting point. It's perfectly OK to adjust slightly.
Often they are larger. It depends on how the carb details. I'm assuming this is not set up with 1:1 linkage.
With the rear plates "open some" are ther secondary transition slots exposed?
I agree unless the secondary t-slots on this carb go low enough to be exposed. That's why I thought it was worth asking.
Perhaps its also worth asking how many turns out the secondary idle mix screws are?
makes it candidate to using 4 corner idle, which you are.
But this is in neutral. That's a good start.
The real test is with a load on it.
There might be a benefit to running a front PV.
IF there is a situation where the mains are starting to contribute fuel other than wide open throttle, a PV should keep it leaner, cleaner and stronger.
I'll leave that discussion to Mderoy and others
Going smaller on IAB will enrich the idle and transition. Opening the idle mix screws may rob the transition slightly but its not guarenteed to go that way.
The reason is transitions slot itself is a variable air bleed and restriction to the fuel in the idle well that is partially mixed with tiny air bubbles.
So its a question of whether the fuel-air in the well is restricted by the t-slot opening when the throttle plate is near the top. If so, reducing restriction to the idle port will allow slightly more fuel.
IAB changes are less sensitive than IFR changes, but dropping just the primaries by .002 is reasonable. This is fine adjustment, not a radical retune.
My experience has been a little different on this point.
I've gone smaller on IAB to successfully enricher a lean transition, but did not observe it to carry it higher in the rpms.
For that (extending into higher rpms) it seems a larger IFR is generally what is needed.
Most of the time when I've gone smaller on IAB I have had to retrim the mix screws, and sometimes slightly adjust the thottle position and the mix screws.
