Board Thread:Questions and Answers/@comment-10797017-20130624101208/@comment-8986886-20130712201526

N-e-ls wrote: Urahara is a master of Kidō. During his fight against Aizen, he could've used Hadō #125 instead of going through the trouble of inventing 2 ad hoc Kidōs beforehand.

Then I suppose Kisuke also could've used Hadô 97, 98, or 99, all which are more powerful than the level 91 he utilized, so that reasoning is flawed at best.