the rope trick is really for molded one piece rubbers, as you found it's difficult with the cut lengths that have a joint - which doesn't actually have to be 'glued' beforehand as Jock does in that series, if cut a bit long and jammed together it'll seal itself well or can be touched up with RTV -
these worked fine with nothing, just make sure you join the lockstrip on the opposite side to the rubber joint
Bill
