You should be able to make it at 6" with little fuss but I'm wondering about your scrap pile now. If you don't have enough to make the blocks at 9"--I don't know how you'll have enough scraps to make enough smaller blocks to make a quilt.
My suggestion would be to just cut out the size squares you need from all your scraps and make the blocks with what you've got then put them away for awhile until you accumulate some more scraps. If you want to finish quicker, start hitting rummage sales & thrift shops for cheap cotton clothing you can cut into scraps.