I was able to replace the standard spur with a Durango one and slipper pads by putting a bearing in the centre of the spur. to get the slipper to lock down properly I had to put a 4mm washer up against the outer slipper plate to make up for the narrower spur gear
Can you clarify your spur/slipper setup? Did you also use the Durango slipper and pads, along with the Durango spur?
What size bearing was required?
Also, for the washer... was that a 4mm spacer, or 4mm OD washer?
If this is s successful setup, I'd be interested in doing the same on a future runner.