I'm nowhere near the elite, so not really in a position to comment, but does carrying an extra layer really slow you down that much that you need to take the risk...?

Carrying an extra layer or two certainly doesn't slow me down enough to warrant taking the risk.

For the record, after suffering last year, I wore an additional base layer, better gloves, and had my vest outside everything, so no messing about with zips at the checkpoints this year. Apart from as Anthony mentions above, being rather hot on the initial run to the Isle Of Skye road, I was much more comfortable generally.

Although I do remember being so knackered at one point whilst somewhere between Upper Booth and Edale, being absolutely out-smarted by a gate for about 30 seconds, too wrecked to work out how to get through it. I guess the fatigue just creeps up on you.