Actually, bio-D doesn't gel like regular diesel. It actually crystalizes. The normal diesel anti-gel additives work to some degree, but still don't eliminate the problem. I think this is the reason bio-D is blended at a maximum 50% with regular diesel.
As for the rubber softening from bio-D, it is well documented in many places. If I knew that viton sealing parts were available to rebuild a Yanmar injection pump, I would be more willing to try it. Maybe I should look further into it.
Any dealers out there know whether viton sealing parts are available for Yanmar injection pumps?