difficult to tell without seeing the body of the quilt.
length will depend on the look you want. I am wondering tho, if your blocks finish at 9.5" and you want to match sizes with your blocks, shoudn't the width of your strips also finish at a combination of 9.5 If two strips equal the 9.5 then the width should be about 4 1/8 finished. Your 4.5" width might finish at a bit smaller than the width of the block. Or is my math head not fully awake this morning.