I would cut the length of the finished strip to match the length
of the sewn pieces, so the blocks match each other when
they are rotated to make the pattern. If they don't come out
to be exactly 6 1/2 it is ok, just so they are as long as they
are wide, then they would match up. Hope that helps. It sounds like your seam allowance might not have come out
to be a scant 1/4 inch, so that is why they are not 6 1/2.