100 lb propane tanks for furnace?

So here's my deal. I heat mainly with wood, and just installed a new 90k 2-stage furnace for back-up heat. The furnace will only be run when the wood stove dies out in the mornings and the occasional weekend I may be gone. I have 1- 100 lb tank hooked to it now to get by and will be getting a second to run both together at the same time. I've seen the charts on how propane will vaporize at different temps, and I am considering building a small shed to house the 2 tanks and running a very small heat run to it to keep the tanks warmer. I want to try to keep the tanks in the 50-70 degree range as this will allow full usage of the propane in the tanks and not allow "freeze up" to occur. Are there any issues I should be aware of in doing this? Thanks in advance!