Cold weather starting,
The 70/30 mix is slow to boil off, the 30% propane will boil off first, so leaving you with a weaker mix.
Use a 4 inch diameter camping gas container that has been emptied and decant neat Propane into it.
Create an outside starting trolly/box with a buggy battery and this container.
The 4 inch dia gives a boil off surface some 15 times greater.
OR
The onboard gas canister should be canted over as much as possible without supplying neat propane gas to the turbine to increase the surface area.
OR
Make your own canister with ribbing/fins
and one last canister, if you must have an onboard canister,and if you have enough room make a canister out of the throw away type, by reducing its height . mine is 2 1/2 " tall ( 8 times boil off surface)
Norman
UK agent for Behotec turbines