I've just fitted my new Harken Clew Sleeve and am experiencing problems getting it to slide back and forth on the boom when adjusting the outhaul. I've rigged it as per the packaging instructions (Hook on port side, line on Starboard). Any ideas on what I could be doing wrong? Perhalps I've opened it up too much when fitting it? Forecast is for a blow tomorrow, so back to the velcro strap!