Tulip Pillowcases

I finished the first 9 of my 18 tulip blocks yesterday.  While I was waiting on my baking project today I sewed them together so that I could make the first of two pillowcases.  In the process, I realized that the instructions for this project could be a little more clear.  For one thing, there's no information about the size of the finished tulip blocks.  They are paper pieced and rather small.  I don't think it's possible to avoid getting at least some distortion on the size of the paper-piecing pattern when it's printed out from a website.  I had "none" checked on my scaling function when I printed them.  Nevertheless, when I measure the pattern on the paper, the block size doesn't measure to a nice even mark on my ruler.  I'd need something with markings at a 32nd of an inch for me to say exactly what size they are.  Further, my sewn blocks are not precisely uniform (are they ever?).  With no information about their size, there's also no clue to help me to trim them. 

I decided I'd trim them to 1/4 inch from the edge of the points where the green meets the black since all seam allowances are supposed to be 1/4 inch.  Then I sewed them together side by side, as instructed.  The resulting strip of tulips is supposed to be 40-1/2 inches long.  Mine is only 39 inches long.  Bummer.  Now I'm a little unsure what to do. 

Figuring I'll think of something to make it work, I read ahead about how to finish the project and found myself completely confused by step 10.  Sometimes these things make more sense as I forge ahead, but right now, it's as clear as mud.  I suppose I could measure the pillows and see if I can make the pillowcase itself a little smaller.  I suppose I could do that.  But instead, I think I'll take a nap.