That is indeed interesting- I can't tell from the pics of the STi v7's if they have the same shape or not.
I'm curious is the threaded portion the same? Does the v7 simply have some more material removed form the piston and squared shoulder, where the v8 has less materail removed and a rounded edge? Are the piston lengths the same?
I have to plead guilty as one of the ones stating the v7's could be used w/ v8 springs by simply swapping rear tops.