front of your helmet as much as you can, or you can do side but make sure your helmet isn't in the frame at all cause that sucks to watch. Chest mounts aren't the best for skiing because when you bend down off a drop or move up and down all you see is your knees. Head mounts let you see more of whats in front of you which is tight. I like 1080 120 or you can do 4K if you like, don't let the frames drop below 60 tho and preferably 120. 240 frames which i think the 7 is capable of will just fill up your memory card and in my opinion it isn't necessary. But yeah a helmet mount and keep your helmet tight so it doesn't shake around and you'll be golden!
