hi I have a sapphire and I have to put the tension up to 9 just for piecing and I still get little dots on back and it makes waves on my edge of the square keep changeing it to fix called the store they say this is normal I thought that good tension is when one color on top one on bottom should not show up on eather side like my old 301. any help out there that has same machine tried all kinds of thread brands and needle mine is a 850 thanks