I have two sets (4 total) of these:
Rola Haul-Your-Might V2 Van Ladder Rack - 2 Bar - Steel - 300 lbs Rola Ladder Racks 59622
Last summer I was hauling around a 14' canoe (strapped to the bars) and a 12.5' Kayak (in a cradle). The vertical pieces of these ladder racks might seem offputting, but they were welcome tie-down points. I mounted the canoe outside the inner 2 and inside the front & rear rack horns which effectively locks it into place before even getting tied down. I took them off for the winter to reduce roof drifts. It is about time to put them back on.
At some point I really should take a picture of those mounted with the boats and four bikes hanging off the back past the spare tire swing-out. Picture being worth a thousand words and all.
But - for hauling a pair of boats and no intentions of getting a RTT, those ladder racks have been just what I needed.