I am only a few seasons in as well so take this with a grain of salt.
I find that things like arms flaping are not the sickness but more of a symptom. For example the other day i noticed that i was getting one arm rotation to balance myself off of jumps. The issue isn't my arms it was that i wasn't perfectly flat based when i left the jump. I had a very slight edge set. After i corrected this i was able to get all of my grabs going.
As others have said you need to be much more compact. Keep your back straight but bend at the knees and at the pelvis. I had a hard time understanding when people told me to keep my back straight but get lower. Don't let your back bow but in the hip area you can bend. I like watching torstein videos as he is quite compact.