In reply to Trossachs:
Look at the Instinct Trail packs. I've been using the X8 for the past year and it's the best race vest I've tried, much better than Inov8, UD, BD, Raidlight, Salomon et al.
The carry is super stable, pockets that work up front and fittings for poles, axes, sleeping bags etc.
It also compresses down well so I can use the same pack for everything from a 50km race to the Cheviot Goat/13 Valleys.