Hi,
I recently bought a Horizon too and was just as frustrated as you seem to be. I went and sat down at the dealer for a quick lesson and learned sooooo much. To FMQ all I do is drop the feed dogs and change to the free motion foot and it works great. I just finished FMQ a small quilt and had no trouble at all. I know it is not what Leah Day suggests and I am sure she knows way more than I do but this works for me. Hope you solve your problem soon because it really is a great machine once you get the hang of it. Let us know what works for you.