Unless there is definitive proof that Yamato is strong, I am not buying Yamato being the Ace of Beast Pirates. She was imprisoned here for 15-20 years and she was never able to escape?!! Because of what?!! A explosive cuff that Luffy is able to remove but she can't?!!
She even thinks that Ace and Luffy are very strong, which we know is not true.
So, until proven otherwise, I am in the group that Yamato isn't very strong. She may be Who's Who level.
[I have been changing my mind a lot lately, aren't I?]