Does anyone have any experience (preferably)/advice re: adding bungee hooks to the top of the "new" (to me at least) BMW system cases? The double-wall construction on the top seems to thwart this as I can't really see where it would be safe to drill for the extra long bolts needed to mount the metal loops for attaching bungees (or other straps to hold a duffle) without running afoul of the case opening/locking mechanism.