I have the Power Solutions dual power adapter and it works great. I am not sure if this company is still in business. The setup they sold is able to be constructed with parts available at home improvement stores though. I bought mine because it was easier and the gentleman at Power Solutions was very helpful, so he deserved the order in my opinion. Like I said, I don't know if they are still in business though.
My EMS allows both compressors to be ran at the same time. Pulls about 27 amps. If something else is turned on, the EMS system turns the 2nd compressor off temporarily. It works really well. But the 2nd shore cord that the dual power adapter provides allows the main shore cord to operate most of the time around 15 amps which means the cord does not scortch as easy. At 27+ amps my shore cord used to get warm/hot at times. With the dual power adapter, that situation has basically gone away.