Don't laugh it is me again the one who bought your frame. I have a friend who has a long arm much like your set up and she used the poly only, she likes the feel of it. She used the medium loft it is the 6mm I believe and I have seen the results. She appears to do a lot of feathering she likes the pouffy look as compared to using the cotton and natural fibers. She tells me to stay away from the walmart brand and buy off the roll as the batting quality is more consistent. You might be making a trip to Fabric land soon