Do I require a washer/spacer/shim between a hub's cone nut and lock nut? When replacing the cones for a front hub with new ones, is it okay to tighten the lock nut directly against the cone nut?  Or must I use some kind of spacer / washer / shim in order for some other reason than spacing?

The reason I ask is that I am replacing the cones on a front hub that was correctly spaced at 100mm.  The old setup has 

Lock nut - Washer - Cone nut - Hub/Cups - Cone nut - Washer - Lock nut


The replacement cones I got match in the old ones in all ways except that they are slightly wider (i.e. take more space of the axle).  So, instead of getting two more cones ($20 more dollars!), I figured I could just leave out the old washers and leave the setup like this, which would be spaced about 100mm:

Lock nut -      New Cone nut - Hub/Cups - New Cone nut      - Lock nut


So, would this be alright?  Does the original washer play any other role than just making the spacing correct?
I've just rebuilt a totally stock Shimano wheel set and it had locknuts touching cones all over the place. Go for it.