I did about a 60% diesel, 40% WVO. Yes, totally right about the viscosity issue-
You can use 80WVO/20 Kero if you wish as well, from what I have heard. Basically since diesel is nothing more than oil with kero, your just making the same blend.
No engine mods whatsoever. I did filter it very well, and used only high quality fried oil. The color was consistant with pictures of bio diesel I've seen, so I wasnt too worried.
however, if you get oil that is about the color of used motor oil, I'd be a little wary of just putting it into the tank. Basically, the viscosity is the key. So if you either A. heat it up, or B. thin it out, you'll be good to go.
But before you take the plunge, let me put on a couple hundred more miles. The engine isnt complaining, it acutally is quieter idling and on cold start. Power is a little bit lower, about 10HP it seems.