James Eaton
Trent Valley Crew
I use the optech utility strap to carry my 600 F4, there are no carabiners or screws - been using for over a year with no problems.
http://optechusa.com/utility-strap-sling.html
I agree, Optech straps are fantastic. I use the standard utility strap on my 400 f4 DO and 300 2.8, and have done for several years without a single issue, just a bit of wear-and-tear, but considering I'm using it, in the tropics, for probably 250 days a year I think is very impressive. I'm still to fathom why people use expensive, flash straps when this is the best I've come across over the years.
James