Ok, one more question on the Holley jetting.

DrCharles said

You lost me here... it's both? If the idle is fine but the t-slot is too rich, won't making the TSR smaller also fix it?

Click to expand...

Yup its both. That's another erason why TSR need is determined later in the tuning process. Of course I had to learn this the hard way myself.

The transfer slot is both a variable air bleed and fuel restriction.
I'll just snip quotes from Tuner here.
the full original is archived here Innovate Motorsp-rts Archive: How do you know what stage of the carb is working?

"The magazine articles tell us the slots obviously deliver more fuel as more of the slot is exposed to the vacuum at the edge of the butterfly and slot is exposed to the manifold vacuum below it. The real deal... is that the portion of slot above the butterfly is air bleed and that below the butterfly is fuel feed. As the throttle blade changes position up and down the slot, the ratio of air bleed to fuel feed changes. As the butterfly opens air bleed is being cut off and fuel feed is being increased. Usually (almost all Holley’s & clones), the slot and the curb idle adjustment are fed by the same idle jet and air bleed.

Ideally, the mixture is richest at the dead idle and then gradually leans as the throttle is opened."

Your engine may be radical enough that a t-slot restriction will be helpful. It should help if its too rich as it transitions into the start of the mains. Trailbeast's engine doesn't seem to be that radical. Rather its pulling hard on the fuel right off of idle.

The full explanation in the link covers the physics.