I think they are are, as you guessed, large thule or yakama and also I am sure quite a few are custome made. if you can get wider (longer) load bars with your Thule you can put more bikes on the roof, but watch your head!
I have a great pic of the Campi neutral support car with rack that hangs down the side on each side with a bike ready to go.
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“One morning you wake up, the girl is gone, the bikes are gone, all that's left behind is a pair of old tires and a tube of tubular glue, all squeezed out"
Sugar "Kane" Kowalczyk