I have reduced my left curve quite a bit from doing PE. At the level it is now it doesn’t bother me, but it used to after I heard some negative comments from girls (in reference to other people’s, not my own).
I only saw the effect after hanging for weeks SD in a chair, with the Bib resting against the chair thus keeping the hanger straight. This made the left CC take the most stress, and it began to even out until both CCs were taking the stress almost equally. This divide and conquer approach was very effective; the Bibster would have been proud. :)
With an upward curve there is no shorter half of the equation, like in my situation, where one CC was longer than the other. So based on this I think your upward curve is safe. I don’t know if I’ve lost any of my upward curve but it’s still quite steep and I can see why people like it and I certainly want to keep mine.