hs backroll and 360 I learned on a trick ski first. It probably took me 3 days of 40 - 50 attempts per day to learn the hs backroll on my trick ski. (I was black and blue like crazy!) Once I took them to the wakeboard, it probably took 2 - 10 attempts to get them down.
Tantrum was a new type of flip for me (no real trick ski equivalent)... I spent 4 - 5 sessions of about 10 - 15 tries / session before I landed my first one. Took a while more to get them consistant.
ts front roll - I hadn't done any type of fronts until this year, but landed a scarecrow on my 5th try! I havent tried the front yet.