I haven't run 39.5 yet, but I have gotten around 5 ball 4or 5 times.
For me it is Technique, patience and confidence.
The more you see the pass, the less weird it will feel. You will be a lot more comfortable, I don't even feel like its 39 because I have gotten used to it.
I definitely watch what I eat, and I ski A LOT. I can only ski about 3 or 4 days a week, but I make every set count.
I think you should try to ski as much as possible, go down to Fl and get coaching for a week, you don't need 6. Shoot 3 days with a great coach can change everything. At 38, 39 and on;the things you do to run those passes are small, and those small changes go a long way.