G'day Don;
http://biodiesel.infopop.cc/eve/ubb.x/a/cfrm/f/898605551 has alot of discussion about blending, however IMHO, to reduce viscosity heat is the best method and the one less likely to leave behind problems.
Set up a two tank system and if you really want to be sure there isn't acumulation or coking run a tank of B100 biodiesel ever 4tth or 5th tank fill.The solvent properties of B100 will clean everything out nicely. This could possibly be even morer important in Di engines as opposed to the IDI ones, from what I have read and understand,as limited as that may be.
The heat will not adversely affect biodiesel as it's flash point is considerably higher than dino, which makes of it's use in the "hot" tank the number one solution to winter geling problems associated with biodiesel in cold climates.
You can set up a two tank system yourself or get it done by "professionals" or order the kit and DIY/have someone do it for you (mechanically incline friend?)
My own two tank system is now in place and I am just working some of the last minute bugs (air in the fuel line), but I am doing it with B100 in it, not vegie ... for the moment.
Whatever you decide be sure that if you plan on running a single tank that it is properly adapted for cold vegie. There are some people out there who do this in a semi to professional way. Do a web search and read everything you can first, then decide.