Doghousemom, it's a hard decision. With black background the star looks more feathered indeed, but if that doesn't match the rest of the blocks I would not do that. With white background it's a beautiful star but not as gorgeous and feathered as with black. So I can't help you here!
The star you made is gorgeous! I love those bright colors. I'm waiting too and I think you're right, each section with a 15" block surrounded by the others. We can do that without them, can't we?!! I didn't start the Granny Compass either as there are still at least 2 mistakes in the latest pattern.