I can't help you with the fixings but holy sh*t they're fat skis!
I thought mine were bad with a 102 waste but they'd look skinny next to those.
I take it you wouldn't want to travel on motorways with them as shown? I'd be worried that the tips would flex under the pressure of the wind when driving at speed. Do you have room on the van floor (or lashed to the ceiling) until you get to resort, when you can fix them outside?