do you HAVE to work at 100% to remove a curve?

is it really that important to work at 100% erection to remove my upward curve?

Unless it is really a pronounced curve upward, I would leave it alone. Use it to your advantage to hit the “G” spot!!!

that seems to be a common response although I would like nothing more than having a perfectly straight penis :)

Doing anything at 100% erection courts injury. You’ve obviously done some reading, why not try what you’ve learned at 80% for a few months (don’t expect instant results) and if it doesn’t work then you’ll have your answer.