unless we play exactly like you, and our bodies are shaped and sized exactly like you, we can't tell you that. somewhere between 18 and 24 lbs is a safe guess since thats recommended by yonex anyway. but anything beyond that, its totally up to what works best for you.
I agree. Personally, I saw the AT800 being strung from 18lb up to 33lb depends on the player's skill / strength / preference. So, no "ideal" answer which apply to everyone.
Best conservative way, is to string it the same as your previous racket that you feel comfortable with, using the same string, tension and stringer (if you don't do it yourself). Then you can really compare. And if you are not happy at that tension as some rackets perform better at particular tension (again, it is personal), you can either play slicing shots (slice-drops / smashes) a lot to break the string or if you are rich, cut it and restring again. And try a different tension. It is not useful to ask others as you chickenpoodle said, it is different for different people.
