Solar wire/cable routing options on my 2005 Four Winds 29Q

Studs... maybe. You should be able to fasten to a plywood underlayment.

From the looks of your roof, and the absence of a TV antenna, I can pretty well deduce there's no existing wires up there for you to use. I guess your drill plan is ok. You can get away with longer wire runs with higher voltage in your array... ie 2 panels in series.