I do timing belts day in day out, and the one thing I have learnt with twin/quad cam engines is to always lock the cam gears in place. It is always better to be safe then sorry. Have seen people end up having a single cam 180 degrees out because a cam gear has spun on them and they have lined it up incorrectly (usually when the cam gear has timing marks 180 degrees apart, like Honda cam gears do)