There are a lot of places that will make you custom certified propane hoses to your specifications (length etc). You can run rubber, or you could run copper? Just keep in mind you will want to have the copper or rubber system tested and certified for insurance purposes (and for personal safety reasons). Keep your lines outside the trailer, as in nowhere near/in/through the sleeping area, and where they go into the kitchen area, make sure it is sealed off from the sleeping area and well vented. Of course, a battery operated LPG leak monitor is a good idea, and they are not onerously expensive.
If it were me, I would do copper with the correct stuff for gas, as well as all the right fittings etc. Then run them to a manifold where you can attach custom (or factory) rubber lines to the stove etc. My friend Mike did this setup and his worked out awesome. All personal opinions of course, it is up to you. Stoked to see this moving along.
Greg