Tom,
I think you are talking about adding oval shims under the WRD as you described in your earlier post. Adding shims will enrich your mixture during WARM UP only.
Usually there are 3 shims under the WRD of different sizes. Over the years I'm sure people have added or removed. Typical sizes of these shims are
.12mm
.63mm
.5mm
.2mm
.1mm
Different combinations of the shims are used to get your desired thickness. I think my 3 shims add up to around 1.2mm (if I remember correctly
) so I would think somewhere between 0mm and 1.2mm to start.
I would also suggest using thin metal to make your shims and trace them from the WRD housing if you don't have an existing shim. You can get the metal sheets from local hardware store. For example, get a .2mm sheet of metal and make 6 x .2mm shims. Maybe try 3 of them at .6mm total to start with and play with it from there.