Following the previous post I have been asked to show a few more details of the roof rack attachment arrangements to see if it could work with other roof bars etc. So here you go:
There are three plates down each side of the rack:
And each bracket has eight bolts arranged in two rows either side of a support bar, although only three in each row line up as you can see here:
On the underside, where it connects to the roof rails there are six L shaped brackets (one for each connection point on the roof rack) that have the nut part of the nut and bolt attached to them:
Hope this helps.