Nope, you don't need a wake at all to do a backroll and tantrum. Those two tricks are all technique. I have done backrolls off a MC wake with about 800lbs and no pole. So you don't have to have a lot of air, just really accentuate your cut away from the boat and be sure to wait until the top of the wake. Take a short hard cut to the top of the wake, if you do it right you will feel the rope kinda snap when you get upside down. You will rotate fast, but don't worry because that's how the trick happens. For the tantrum you have to stop your edge abruptly at the top of the wake and throw your head and shoulders back. The tantrum may be a bit more difficult, but you can do it.