After you get the parts weighed to calculate the actual bobweight needed,
then you can estimate where to start with counterweight diameter. The shop will likely have to go back and forth from cutting some off the counterweights, check the bobweight, and cut some more. Then do final balancing with the regular drill method.

I expect starting with counterweights at 7.31" dia would be safe, assuming the parts require a bobweight below 2300 grams.
Then maybe try 7.25" dia.
This is my Callies 4.250" stroke crank, before cutting the counter weights down to around 7.14" dia (bobweight 2185 in a low deck with 6.535" rods).