Air shocks have come a long way in the last 5 years alone but even on the best of them there are still stiction issues that you just don't get with a coil spring. Coil shocks are much better suited to Fort Bill due to the brutal nature and length of the track. It's worth noting that Mick Hannah was also running a full carbon frame which would absorb more of the vibration caused by the constant punishment which that course dishes out. Would he have chosen the Vivid air if he'd been on a full Alloy frame...? Who knows? It's a bike wrecker, just look at the amount of punctures over the weekend! I'm pretty sure Peaty will use the Vivid air whenever he thinks it will offer an advantage over the coil Vivid, just as it did in Canberra.
And Rolo, don't take it the wrong way but by your own admission you're not going to push it's limits, so I think you'll be fine. Unless you fasten your shoelaces and then we'll be in for a bumpy ride!
Sort of, the front triangle is carbon, the swingarm and lower link to which the shock is mounted is still alloy. The GT Fury has a carbon mainframe and swingarm. Both ends of the shock are mounted to these parts. I've rode a Fury and it has very different charictaristics to the previous GT Dhi. It's hard to put into words but it just feels 'smoother'.
In an interview with Marc Beaumont he said that Mic Hannah was using the air shock as he as an over the front style, putting less strain on the shock making it viable.