I checked with Aldila and they show nothing they have that has “NV-3″ that they built for Cobra. Their advise was to trim 1/2″ increments from the tip from the 3-PW. Since you have the 4, you would start with 1″ for the 4, 1.5″ for the 5, etc. Personally, I would start with the 1/2″ for the #4, 1″ for the #5, etc. That is the trim instructions for the NV iron that we sell that is a 40” .370 parallel tip shaft. sounds like yours is more similar to that and it is safer to start the trim with the 1/2 inch on the #4 since we do not know exactly what the parallel tip section length is. After tip trimming, install in the heads and after the epoxy cures you can cut to your final playing length from the butt end of the shaft.