The metal tips are very durable. I've seen some brand new netal ones for $275 on Ebay recently, more than once. I'm thinking I'm glad I got rid of the pair that I sold before these appeared. The ones I had (and still have one more set) are actually Bird dog wing tips of a different part number, but are physically identical to the civilian ones. I have a Grimes strobe set piggybacked on my old E series nav lites and yes they work great and look good too, on the metal tips on my '59.
Remember, these tips have no redeeming qualities other than durability and decent looks. They don't do anything special as far as aerodynamics goes, they just cover the end of the wing. A big flat endplate will do more than these tips will. Its really up to your mechanic.
Charles
