Start the Mar-Tacks a little outboard of where you think they should be (if you use the grease method of marking how far the axle goes in). Grind flat, insert through old axle seal, see how it lines up, add a tad if necessary. Um, easier to add more tack than remove from splines because your axle sticks out just a little too far...

When its all spiffy, replace the axle seals with fresh ones, grease the axle to slide through, and assemble.

Ask me how I found out about this... <img src="/forums/images/graemlins/rolleyes.gif" alt="" />
I do have some trail spare axles now, though...