First, I don't know where they said make it 2" smaller - that is just too much pillow for the space. I cut my fabric 3/4" to 1" larger than the form depending on how firm I want the finished pillow, sew 1/2" seams and then do a second row of stitching to reinforce (lots of boys in my family and they can be rough with pillows!). I usually do the envelope style because I have to wash them often (same reason!). This makes the pillow form snug and fills the corners. One tool I use for so many things to push into tight spots is a chopstick. They are long and have a blunt end so they don't poke through fabric. Not sure how you could make yours fit now - either find a way to stitch two sides of the form a bit smaller or add a small border to the front of your cover.