Since I have yet to achieve the 1/4 inch seam, these words are really from an advanced learner. I stopped worrying about how big the blocks should be unless I am having a swap with someone. Since I am making all of the blocks and they are "off" a bit they will probably be off by the same amount. If I need the quilt to be larger, I just add another row.
I realize that this does not answer your question, however I hope it helps you to not worry about having things be perfect.