I don't mean to rain on the parade... But it seems to me like you went to a lot of work that could have been avoided, by simply interrupting the injector fuse at the fuse block... If the xB doesn't have an injector fuse at the block, though, feel free to ignore my ignorance...
And I don't know how you hold the stick, but I usually drive with my hand around the circumference, and would therefore install the switch into the head of the shifter knob. Just my $.02