Thanks for the info! I also posted a note on KTMTalk to see if anyone has made the wheel work. I will let you know what I find out.
On my '06 wheel with the '06 backing plate (p/n ending in 344, not 144) I could not get the backing plate to squeeze into the wheel with the cushion rubbers installed. I used the axle, axle nut and some tubing "spacers" to draw the whole thing together. You got 3mm, which would be tight but it would work (you did it) and I got 8 to 9 mm of backing plate sticking out. No go.
I will try your part numbers and see what I can come up with!