2003-2006 Tourer Roof Rails - Suitability For Sea Kayaks?

[merlinz]

I'm seriously considering buying an Avensis wagon as our next vehicle for reasons of safety, comfort, reliability. We occasionally carry a couple of sea kayaks, for which we use Thule aero bars and Thule kayak cradles. Having dependable roof rails is a priority because we don't want the kayaks coming off the car. They're not particularly heavy but they must create a significant wind load. The Avensis rails seem just long enough (the kayaks are about 5m long, so the longitudinal separation of the cradles is important for stability). The plastic covers at the ends of the rails seem rather flimsy, in fact I noticed one missing from a vehicle here recently, but the rails themselves feel reasonably strong even though they look almost as though they might be made of plastic. Does anyone know anything about the composition and strength of the rails, their rated load capacity, and suitability for this purpose? Speed limit in NZ is 100 km/hr.