I don't know how having both arms straight or bent/straight or both bent relates to topspin production of the 2hbh?
Some people say having both arms bent (or at least one arm bent) increases topspin? Having said that, Simon is double bent, and hit a flat shot...
...Whereas Nadal is pretty much double straight arm, yet is the only pro on tour currently I see hitting with a windshield-wipe finish on his backhands. Despite this, his backhand is nowhere near as heavy as his forehand, and his inability to get the ball kicking way up in his opponent's face was evident against Zeballos, a lefty with a 1hbh.
Here's Nadal hitting backhands so you can see his WW finish;
Do you guys think Bruguera and/or Gulbis hit heavier 2hbh's than Nadal? Bruguera and Gulbis are some other players brought up in conversation when talking about heavy topspin 2hbh's.
Neither Bruguera or Gulbis use a WW finish. Gulbis uses a 'pat-the-dog' type of takeback, however.
And I have no idea what about Bruguera's stroke made his backhand so heavy... Would be grateful if anyone knew...