I like the point that you get your "own" number! - So if I were to decide, I would make it two options for the size of blocks! One where you get your own "perhaps-prime" number! And one where you get the smaller, and thus more efficient blocks (I guess it is quite fine with standard size of these blocks!).i've thought about having it be user defined, which wouldn't be too hard, but i think that deminishes the point of comparing block times a bit.