the one time i leave northstar to go to mammoth, if you do find someone to go with go to lookout mountain and the martis lift, at the top of the lift take a left and just go straight into those trees ski down a little bit and theres a cat track thats perfect to build a jump on me and my friends built one last year ill post the vid below, we built it in a half an hour and were kinda lazy in building it so its not that big but you def could make it pretty large