I gave up on my plans for a 6dof flight sim platform for this very reason. I'm now working on a non moving G-Seat instead.
Work has previously been done on your issue. Although I think it was with DK1. Have a look here viewtopic.php?f=29&t=7933
how did you get it working while driving the vehicle, as posted in your blog?
I use a 2dof motion sim with the dk2 and I don't have any issues with that at all. I can crank the motion right up and it all stays smooth. I don't though as you only need smaller movements in vr. I did turn the bump simulation down a bit as it shook the screen too much.
I've been dk2 and motion driving in iracing for months now.