the strap points line up spot on, i have sewn a couple of bits of velcro strip through the bits on the bag so i can hook the velcro loops over the cradle to hold it while i do the straps up.
Perfect, that's what I have already! Was thinking of going for the double ended to make it easier to get loaded centrally, but I'll try it with the Xtra first.
Which drybag? Do the strapping points on the alpkit bags roughly line up with the cradle? This was my plan too.