As a contractor and as a handyman, I've had too many jobs where "the customer supplies all the parts" go bad, all the parts aren't there, the customer doesn't know what is necessary, and starting a job and having to go on a parts hunt or come back at a later date drives my costs and travel time up.
You either know what you are doing, design it yourself, and the laborer, unlicensed provides the grunt work, for cheap, or you don't know what you are doing, hire a licensed professional, pay for their expertise, and do the job right, the first time.
400 watts for a 5th wheel, most of them that I see are 30 feet plus in length, sounds like too little, to me, especially for winter time use.
This is a half baked idea. You're gonna get what you paid for. Not much. No one here has seen your 5th wheel, getting pricing over the internet, as such, is a complete joke.
As an aside, as a general contractor that has built a few custom homes, and done plenty of remodels, my Travel trailer was built by Amish employees in Michigan. Their work is no better than stuff built by Mexicans by Eclipse in Riverside, CA, or Mexicans at Lance in Lancaster CA, none of which speak English as a first language. The quality of construction by them is junk, mass produced cr@p. Built to a price point, and built to fail within a decade or a bit longer.
A few trades they suck at are plumbing, electrical, cabinetry and finish carpentry, IMHO. They have dangerously low standards on electrical in particular. Don't ask me how I know.
