haha think it will be hard to get an answer from a pro player
Depends on what kind of serve and for what kind of return:
- for both short push and flip, more open angle in beginning and close depending how much backspin. More backspin, more open angle.
- Open against long push, need more open angle compared to backside because the short pimples do not brush as well but like backside you can have more closed if you are able to brush fast. As well adjust according to the point above for push and flip.