Four Kayaks, One Roof

I can be delighted by the strangest things. Take this van parked in Tiso's car park, Inverness.

We're getting a van like this at the end of November, but Liz and I can't agree the size of Kari-Tek roof rack we should buy. She says it should be wide enough for two boats, three at most, because that's all we'll carry.
I say it should be able to take four, in case we want to shuttle with another pair. Liz insisted the bars, big enough for four, would stick out past the sides of the van.
Then I saw this van, with a four kayak rig, which did not stick out past the side of the van. 'Perfect', I thought, 'this will convince Liz'.
Wrong. We still can't agree the size to buy.