I take it your going carbon fiber since the chart doesnt go to the length you want?
in this link an aluminum 4" can take 2k hp and this is what Mark williams wanted to sell me 1st at my length so at 1/2 the $ of cf this works for me even with shipping 50$ maybe. aluminum ds spec from the link"Description 3.5″ Shaft with, 1350 Series “Gold” Cryo treated Solid U-joints, are built under the most Stringent Tolerances in the industry. Tubing is Factory Straightened to .010″ total runout at the center of the tube. Tube yokes are welded to within .006″ runout on each end. The shafts are Electronically Computer Balanced to less than 1/8 Oz/Inch, as an assembly, assuring smooth operation at the Big end as well out of the hole.
Critical Speed is calculated on each shaft to insure your Safety and Ultimate Shaft longevity. We recommend the 3.5″ shaft in most cases to 1000 Horse Power. 4″ Shafts are recommended to 2000 Horse Power.
Shafts are complete with the most common standard transmission Slip Yokes. In some cases an upgrade on the Slip Yoke or U- joints may be considered."
