Irvin, TBH I don't think the 10% pre-stretch is needed. I'd prefer to stick to a few pound more so that those strings are set at a constant tension.
With squash stringing one tends to use low tensions, around 22-28lbs. 10% would make little impact as you'd only be adding on ~2lbs before settling back at the usual tension.
Head IG Prestige MP; USRSA MRT, Wimbledon stringing team since '04; Babolat stringing team '10-'13. Twitter - @therqtstringer