Hi,
I have a double long board coffin bag. It's from ocean and earth, it is advertised for two but can actually take 3 longboards. I have used it to go the morocco last Easter, boards arrived safely. It has 20mm side wall which is twice as thick as the industry average. Since then I have used it a few times to transport the boards on the roof of my van.
I live in hassocks near Brighton. It cost me £220 but ill sell it for half that. Perfect condition.
Adam