Pascal,

Gary Lee's stuff is *HIGHLY* recommended.

My setup has two Yakima 'Viper' trays and one
'Boa'

What you put on there really depends upon
your mtn. bike fork.

The tubing he uses is a bit 'thinner' (to help
keep the weight down) but he includes some
'shimming' material that works really nicely.

It does make the hatch a bit heavier, but not
too bad in practice.   I see that he's even made
them a bit lighter now as well.

I can haul 3 fullsize mtn bikes on mine just fine.

Photos here: (my van is on Garys site.. second link)
http://tims.homeunix.net:8080/~tims/gallery/VW
http://www.telusplanet.net/public/gary2a/rack/4bike/widepage10pics.htm

Gary has all the details on his website here:
http://www.telusplanet.net/public/gary2a/rack/rack.htm

hope this helps..

 -tim