The really nice thing about paper piecing is that you don't have to worry about exact cutting. You cut oversize and then trim after you have sewn it to the other parts of the block.
It's interesting that you mention Carol Doak, BellaBoo ! We are taking her Sensational Nine Patch Stars class on Monday. We've been registered for a month and we got the last two spots in a class of 20. It should be great!