I think the size range may be an issue. 20' trailers are usually seen as starter trailers. I see 20' trailers advertised for $10k occasionally and midlevel up to around $20k. I suspect you will have a tough time building a high quality unit to compete at those prices.
I haven't come across a lot of high end trailers in that size range. Usually, once buyers want high end they are over 30' long and then the price does go up substantially.
Slideouts will be a key issue. Without those you really limit your market but they make it much more complicated creating a truely sealed unit.
You might look at bumping up into the 28-35' range. I think that will give you a lot more pricing flexibility as you have larger base of potential buyers.
You might also consider the 5th wheel market as high end buyers tend to gravitate towards 5th wheels over travel trailers.
What kind of interiors do you have on the boats you build? If they are simple fishing boats with minimalist interiors that take up less than 50% of the boat, that likely won't cut it in the RV market.
Do you have access to bulk pricing on RV style appliances? If you have to pay retail prices, that will drive your prices up.
I wish you well and keep reporting back but I suspect there is a reason there aren't a bunch of small builders doing this.
