Now that I've actually thought about it some more, I don't think the washer trick will help. The clearance problem is between the bottom washer in the stack, the cup shaped one, and the shoulder on the driveshaft. Flipping the thrust washers will make the stack a little higher, but won't move the bottom washer away from the driveshaft. Best bet is to just run a spur that uses the 1/8 diff balls I guess. I'll order some RW spurs when my current set up needs an overhaul.