Radiant heat in my travel trailer

Ian_5

Hey you guys, i have a 1953 33 ft spartan aircraft spartanette travel trailer that i am completely redoing in hopes to move to colorado. i am planning on having a solar heater for the pre heat, and a tankless heater for the primary heat. the trailer will be insulated with spray foam and i plan on having it very well insulated. i will use 1/2" pex probably, it will be an open system so the tubing will act as a small holding tank for water, i will also have a few small radiators in various places around the camper that are tied into the pex. i will use propane to power the heater with. i am wondering if this tankless system is the best idea, some say it is, and some say they loose a lot of efficiency when the water that is being returned to it is hot. i am mainly asking for any advice. thanks, a lot, ian