I don't drop the feed dogs and I get a much nicer stitch. I use either the teflon slider or better yet a piece of clear vinyl that I purchase from wal-mart .. Cut the size you want to cover over the bed of the machine and make an opening big enough for the needle to go through the vinyl, keeping the feed dogs covered with the vinyl. Tape the vinyl down with clear shipping tape or lately I'm using blue painters tape just to keep it flat when moving the quilt around. Leah Day has very good tips and videos on her site I think it is daystyledesigns.com. Not positive on that but try it and watch some of her videos, they are so helpful. When doing a large quilt I cover a big share of my table with vinyl.
Suzy