Myself and just about everyone i know here uses single line for Ropewalking (ascending) gear, and doubled line for footlocking, usually backed up with an extra long 2 or often 3 wrap prussik, sometimes threaded under your shirt to keep it out the way. I generally use footlocking for spikeless ascents from 5 to about 12 or so metres (depending how fit i feel!) and ascending gear for higher climbs. I find the doubled rope for footlocking gives an easier grip, and you can quite often have your usual climbing system installed beforehand on the ground, with a bit of shuffling of the footlock prussik your good to go.