I added the Supco SPP6E to my last trailer with a Coleman MachIII. It has worked very well for well over 10 years. I've read lots of negative comments about it, but spoke to an HVAC professional before I bought it. I'd do it again in a heart beat.
I added Micro Air Easy Start to my Dometic Brisk Air 15k BTU A/C. It works very well with my Champion 3400 watt inverter gen. It costs quite a bit more than a hardstart kit though.
2015 Ram 1500
2022 Grand Design Imagine XLS 22RBE