I free motion with my 66 alot. I just put a piece of vinyl over the dogs and make a hole only big enough for the needle to go through tape it down with shipping tape and your ready to go. Get my vinyl at wal-mart by the yard, very reasonably priced. I also have some supreme sliders, but just sliced one pretty bad taking it off the 66. The needle cut it as if it was a slice of meat as I was removing it. Now will use my vinyl for a while. The sliders are too expensive to be careless like I was. Try the vinyl you'll like it. It covers the feed dogs and your stitches are good on front and back.
Good Luck
Suzy