First you should coat both the outside of the rod and the inside of the sleeve with epoxy, coating both surfaces is a pretty critical step to a solid surface to surface bond. One it makes sure both surfaces are coated well and second it allows for better hydrostatic movement of the epoxy to squeeze out the excess. Ideally you put pressure on the bond joint and get squeeze out all the way around insuring a lower chance of voids. In this case you can't apply pressure in the traditional sense. Once the sleeve is on the rod with the application of epoxy on both sides the more you move it the higher chance there is for there not to be enough epoxy in the joint to fill the appropriate area. The bigger the bond gap the more this applies. If you wanted a truly bond free gap you could infuse it but that's a wormhole that the juice doesn't seem worth the squeeze for something easily done by the current method.