Propane flow at that temp should not have been much of an issue. IF you really want to heat your propane tanks go to a hot rod shop and get 2 nitrous bottle heaters. They work on 12V and keep your tanks at a warmer temp.. a magnetic block type heater might just be too much heat.
2004 Chev Silverado Duramax optioned past the max. 2009 Jayco Eagle 308 RLS 765 watts of solar, 6-6 volt batteries (696 amp hour), 2000 watt (4000 surge) whole house inverter.
140 days boondocking in 2016
211/2015, 196/14, 247/13, 193/12