tank bag

Hey all I am new here learning my way around the forum :) I own an R1250GSA. I was wondering if anyone has experience with the Sw Motech Pro City WP. I am looking for a good Waterproof tank bag that doesn't involve the straps that is completely waterproof. Has anyone been using the SW Motech...

new GSA coming next month so im looking for a tank bag seen this givi one which appears to tick all the boxes and at a reasonable price too. does anyone use one already ? any comments please. also "strap on" or tanklock ?? thank you http://www.givi.co.uk/soft-bags/Tank%20Bags/XS308%20TANKLOCK