Offer withdrawn then (he can still have a Bergen though). Pitch tent and just play with tarp configurations and problems solved. I don't want to see the lad wet and cold until his skills prevent this.
Why worry if he gets wet and cold, he's young, fit and healthy so it's highly unlikely he'll come to any great harm.
Bit harsh I know but it's not as if it's winter conditions now and getting it wrong is a great learning experience to make you get it right next time.