well i do believe more than 30% chakra can be placed in the clone and to prove kisame said "we only placed 30% chakra into them", it was a bold statement giving us our answer.
Know some things to think about...

-with 30% chakra into the clone, what about the clones chakra, does their chakra add to the 30%?
-why is itachi so strong, he isn't a jinchuuri (sorry for spelling) nor did he so something like sasuke did, so why is he so strong?
-One of the clones is from the sand village, he was there for four years, and when the old lady said something about when the clone joined the sand vill. the timing was just right when akatsuki was making their move or something like that, does that mean the clone was under control the whole time or was he a spy for akatsuki not being controlled?