Hi

I think that is very clear about the temperature, and there are many experiments you can run to test it out in your kitchen.

I totally agree that a double tank conversion is the best way, in my case I drive about 5 miles to go work, I put a tarp in front of the radiator, and by the time I getting to work the car is at working temperature, thats like 10 minutes, so I wouldn't be practical for me at this point to have a double tank system, or leave the car idling 5 minutes for a 10 minutes drive.
There are other things to consider, in this case is a Mercedes 240D with a inline IP, there are almost no rubber gaskets or seals, it has a pre-combustion chamber, this is very different from a WV TDI or a common rail, or other injection system that could be more sensitive to the fuel type. That is also I'm trying with the pump in the bench, seeing different fuel spray performances.