The 2-3 overlap is a pet peeve of mine and I have done a bunch of the restrictors. Some guys use brass pipe plugs after threading the orifice. I use a 3/8 core plug (like a mini freeze plug). Dorman #555-115. You may have to drill the orifice a bit to get the plug in.

On a street car, it is difficult to get ALL the slap out when idling around town. Light load and low speed reveal the slap from 2 to 3 the most. If you want it all out on a street car, the best way is to start with a small hole in the plug (.070" or so usually) to the point that there is a flair up between the 2-3 shift. Then keep opening up the hole until the flair up just stops. But that requires repeated dropping of the valve body. That is the way I do mine; start small enough to have a flair up and gradually get larger till there is no flair under load and little or no slap at light load, low speed.

For those that do not particularly want to repeatedly drop the valve body, .090" will usually get you close. But it does vary a little from tranny to tranny.

At the risk of getting flamed, I will make a suggestion should you decide to start with a small hole and gradually work your way up. I just put some stiff grease on the drill bit each time I go a bit larger and just leave the same plug in the orifice. Then, spray a good amount of carb cleaner or brake clean or similar product and then hit the plug with some air. Gets the chips out for me.

If you do need to pull the core plug, you can just screw in a sheet metal screw and pull the plug with a claw hammer or something similar.

All it takes is some time and patience to get all (or most) of the 2-3 overlap out.