My upgrade ideas
Tricks: if you press buttons in a certain combonation, for example: up, up, down, down, in the air then you will perform a trick, giving you boost.
Boost: If you upgrade your boost, then when you do a flip it will give you more boost then you would have if you did'nt have it upgraded.
Sled: i think there should be multiple upgrades for the sled, for example: max speed, aceleration, and controlablity in mid-air.
Requirements: I think there should be multiple levels for each upgrade, but to get them, you must meet certain requirements for each level, perhaps it could be something like, level 1 upgrade requirements: less than 20 minutes Time total, level 2: less than 18 minutes, and level 3: less than 16 minutes.
Bring me my umbrella, I'm heading to the moon!