We typically do not camp in weather below 40 degrees. We have camped when it got down to 29 or so with no issues for a short time. Our tanks are under the floor, and encompass much of the underside of the trailer between 2 grey tanks, one fresh tank, and one black tank, so there's not much room for insulation anyway. We do not have our tanks heated.
Dingo Girl: we have had no "shift" traveling with things attached to walls. Our recliners are attached to the floor with elongated holes for the bolts, and have not shifted. The refrigerator cabinet is also attached to the floor for safety. Everything else is attached to walls only with aluminum rivets through aluminum tabs into the ribs. Piano hinges were used at the top of the upper cabinets to fasten to the walls. It's all in our thread, "Little Girl Refurb". We did it this way per advice we received at the Four Corners Restoration Rally a few years ago by a high end restorer from southern Ca, Uwe at Area 63 Productions. He is also the one who suggested the floating cork floor we went with. Good Luck!