I might suggest getting a different cover. The fairly ubiquitous in the US Dowco Guardian covers have vents in the top with little flaps that let wind blow through the cover, but keep water out. I live in southern Wyoming where high winds are a daily occurrence for half the year and even in 60+mph winds to the side of the bike its never tipped over.
Hey Weljo, did those non-stock mirrors improve the mirrior vibration at all? I got mirror extenders which greatly improved what I can see out of the stock mirrors (not just my elbows anymore), but you still see mostly blurry vibrating objects in them at speed.