Seems like any side should work. Even if your initial 2 strips were different widths (I don't think you would get the effect where all the seams perfectly match, but that could still look cool). The important part seems to be that your final tube, the top strip equals the width of the 2 bottom strips, to give you that half square triangle effect.
And I understand wanting to play hooky to do this. Most of my supplies are packed up, so I can't do this until January :( but I want to!! :D