Replying to Knees bent on rails or not?

I have been skiing rails for a while, I can do some basic stuff like f2, b2, fs, small backslides and stuff. The thing I struggle with most is staying on rails, I feel like if i dont hop on perfect I cant ever adjust or do that shoulder-ski rock stuff. I see some people say knees bent, some say not. What is the best for balance? I dont have centermounted bindings cause I ski outside the park, but they arent far just a couple cm back. Any other tips besides obviously centermounting?