Our LP tank is located just behind the coach's left/front tire. I connected two 12 foot sections of high pressure LP hose together, and routed them from the tank to the other side of the RV. They run under the RV, but above the frame, so they're protected from road hazards while driving. When the BBQ is not in use, about 10 feet of the other end of that hose is coiled up in the basement storage compartment that's right behind the coach's right/front tire. In the first image, you can see where the hose comes into the compartment, and how it's coiled up and out of the way. When I need it, I uncoil it and route it through an already-present access hole that's there for an electrical outlet. Works great.
When plumbing the Big Buddy heater, I used a diamond tipped hole cutter to drill a hole in the tile floor, just behind the driver's seat, up against the left side interior wall. You can see it in the second image. The Big Buddy's regulator is at the LP tank, so there's only low pressure propane coming into the RV. I have about six feet of hose inside the RV to move the heater around. I could attach more, but never found that necessary.
Kev