I usually use 1/2 the size of the square to determine how large to cut my corners.......so for myself I would use just cut my 4.5 in squares into 4 quarters that should be 2 1/4 in each. I'm sure someone with much more experience and more matmatically sound advice will be along shortly to give you the correct answer. Cant wait to see your finished project, Bow tie is on my bucket list!