There are way too many threads on "flex" and "upright boots" for me to get a real answer.
I'm skiing on Krypton Cross boots. No fit issues. Canting, cuff adjustments and boot sole planing were all taken care of by Billy Kaplan. I really don't remember any fore/aft adjustments being made.
I have (due to medical issues) VERY limited dorsiflection. 5'9" and 180ish lbs. Based on everything I read, I should be in a rather upright/stiff boot. Since these boots are easily adjusted, I've played with this ad nauseum.
For the life of me, I can't seem to ski them when either very upright nor stiff. Is that pure technique issues? I am most comfortable with the boots in the softest (90) setting with the small wedge in the back, so mid forward lean
My issue is not being able to engage the tips. The downside, when my boots are in the current position, is when the speeds really pick up. At that point, I do prefer some added stiffness. I'm skiing on Kastle MX78's with Dynastar PX 12's if that matters.
One last point. When I have made changes, I almost always switch it back after a couple of hours. Do I need to ski them that way longer to readjust myself?