That is correct Fred, where your showing, because if you dont put that 3/16" spacer on the axle, the chain will be just a bit out of aline with the front sprocket. If that spacer not used, it might run like that ok, but would probably wear the sprockets more on one side & a lot more attention would need be paid to keep the chain tight.
On my daughters R, hers has a chain guide on the swingarm & the chain was out of aline enough it was rubbing one side of the plastic guide.
What are those 400EX Tusk axles going for now ?.
Ohhhh, you'll also find even with using the extended type 400EX hubs, the 400EX extended axle is 1" shorter than the Lonestar +4. That 1/2" narrower on each side didnt bother us though, just tightened the ol girl up in the corners a bit more.
Neil