David,

I live at Coffs Harbour and had considered using radiata pine for my kayak but decided against it due to both the weight factor and radiata's lower longitudal strenght compared to WRC. I don't know where you live but I sourced my cedar from Cedar Sales at Archerfield in Brisbane. The staff deal with a lot of kayak/boat builders and will normally allow you to sort through stacks of 100x25x5400 (4inchx1inchx18ft)timber to chose what you are after. I chose 3 pale yellow and 1 chocolate brown board for $35aud each. Other capital cities would likely have similar importers of WRC so it might be worth looking around instead of using the lesser radiata.