*clears throat* "Ahem!"
"ZESUUUUUU!~"
EDIT:
The idea I had in mind for all this was pretty simple; weight doesn't factor into how strong the Rippers are. Just because they're lighter than a Hostile, doesn't mean that they're also physically weaker. Instead, I believe that they should be stronger, much like how an insect has a significantly superior power to weight ratio than we do. In my opinion, Rita was able to take the arm out not because she damaged the Zesu or anything, but because she popped it out of it's joint before the dull minded Ripper could understand what she was trying to do.
Either way, Sigma's back in command, so I look forward to being a player again. Now, what to write....