That's darn cold, Pete. Eight degrees for 3 days should freeze the balls off a brass monkey so I'm not surprised the plumbing bummed out.
In our experience, with the coldest we've been in around the mid to low 20's, if the interior temps are comfortable the spaces between the hulls are OK. I have a system of eight temperature sensors installed in and around the OO-II with three between the hulls that all transmit to a single console so I can monitor them at a glance.
FYI everybody, wind chill has no effect on inanimate objects. The trailer will never go below ambient outside temperature no matter the wind speed. However the wind speed will affect how rapidly the temperature of an object will reach ambient.