Yeah, was afraid of that. 4 lbs with parallel-flow condenser/evap is WAY too much refrigerant. With your mix-n-match components, really don't have an exact amount of charge to give you.
As to reaching Bill, best way is to call. He recently sold off the aircon part of his business to a company in Chandler, AZ, but he will still provide tech support. That said, I doubt he knows exact refrigerant charge with those components either.
The best way to charge a 'frankenstein' system like this is via condenser subcooling and evaporator superheat. Google those terms to learn more about that. Most A/C-refrigeration companies will have the tools to measure those values in real-time. I fine-tuned the charge level in my PlaneKool system using these bluetooth probes:
https://trutechtools.com/JL3KH6. I had initially charged via observed pressures on a manifold-gauge set, but turns out I had left significant performance on the table without knowing superheat/subcooling.
Values you're looking for are ~5 deg F condenser subcooling and 5-10 deg F evap superheat. Weigh in the charge so that you'll know in the future how much refrigerant your system takes. Best if you take the refrigeration tech on a flight and measure/charge while airborne. Not enough condenser airflow on the ground to get meaningful results.
And, because there are so many variations of AS systems out there now, you can't just charge to some level that's been published. With the original, copper round-tube systems, okay, but you don't have that.
