Last summer we had an Amish oooling coil installed in our Norcold 1211 unit by JC Refrigeration in Shipshewanna, IN.they actually make the units there and install as well. They know proper installation is critical and that is what they do. They also will put fans on the top cooling fins if you want, and at our request installed a halon fire extinguisher in the outside compartment and a circulation fan on the inside. We also opted for helium gas rather than hydrogen to charge the system out of safety considerations .
To say it works well is an understatement. JR at JC refrigeration is fantastic. No more frozen lettuce in the bottom drawer and temps are now even throughout the inside compartment based on careful temp measurements I did. We had to keep lowering the temp setting from the 5-6 we were using to 2-3 now to maintain 38-40 deg in the main compartmen after the conversion.
Be careful, there are some outfits that claim to be “Amish” and may well be, but they do not make entirely new units specifically designed for your refer and the use of helium, but only remove, pressure check and recharge your existing coil.