The 2 most recomended and used shaft materials are Aquamet 22 and K Monel. In high HP boats I will only use K Monel. In my DiMarco 21 with a projected 2500 HP it will be getting an 11/8" shaft of K Monel. With the source of these materials coming into play because of all the cheap shit coming out of China, you have to be extremely dilligent when sourcing a supplier. At this year's Enduro there were 4 propshaft failures all new shafts and all from the same supplier. 3 were material failures and 1 was caused by a thrown propshaft blade. All were 1" Aquamet 22 shafts. There are only 2 K Monel manufactures and/or distributors in the US and their base material is sourced from China. The GOOD K Monel shafts come from Italy and are made totally in Italy but are very pricy at about 1800.00 for a cruiser length shaft. Cheap really if you are running a Grose prop!!!! Whip struts, forget about it! Drag boats, 1" shaft, K Monel if you love you're prop. BAF, BAH,BFH 11/4" at least K Monel. I had a strut failure in my DiMarco 21' going 100-mph with an 11/8" K Monel shaft that was off of one of Sonny's race boats orignally and after about 15 years running it. It tried real hard to router it's way thru the bottom of the boat but got everything under control and idiled the boat about 2 miles back to the ramp on the Delta. That shaft was only bent from the strut end back and I still use it today to bore propshaft holes in the bottom of new boats and the prop suffered no damage whatsoever!!!!!!! My 2 fingers are tired again, time to move on1