After commuting all winter with my rucksack I decided to get a pannier rack whilst on offer. I've got a seat post one which, at first was difficult to mount with enough wheel clearance from the bags so ended up with it high up on my seat post. It was secure vertically but kept on twisting around. I had the qr fairly tight but can't work out where I'm going wrong. I wondered about more/thicker rubber tubing wrapped around seat post? Any thoughts from anyone using one of these?