An integral part of a quality pump rebuild is to verify shaft straightness, and then take a truing cut (usually several) to the shaft where the rope seal runs. We use a crankshaft polisher and a lathe to polish the shaft to a very fine finish before the shafts reinstallation. If the shaft is only polished and not trued first, the new rope seals life will be shortened because the worn shaft will still not be totally round or true to the shafts center. Remember that the stock stuff lasts 20 or 30 years with proper care and maintenance, but then again the new shaft was true and factory polished. If you don't true and then polish the shaft during the rebuild, in some cases the new rope seal can destroy itself in several outings. Since the rope seals typically last 20 to 30+ years, their replacement with anything else in MY opinion is just an elegant solution to a non-existant problem. Its true, that rope seals do have a few horsepower more loss from drag, but since a jet requires 20 HP per MPH gain anyway, and I am not chasing any national records, I still don't care. You still should true and polish the shaft before using a lip seal retrofit kit to ensure a long service life. Every shop has their own way of doing things, this is how we choose to do it. We have had excellent results. As far as seal material goes, both types work well when installed correctly. We also like billet inducers, real boobs, green eyed redheads, fast cars, motorcycles, boats, and jumping out of perfectly good airplanes. What the heck do I know. Everything here is just an opinion. TIMINATOR