Hmmmm.....I'm unfamiliar with this machine. If it doesn't allow you to set it all the way to 0, and you don't want to actually lower the feed dogs, if you are going to use a supreme slider or other slippery mat over the dogs, it shouldn't tear the mat up and will keep the dogs from grabbing the quilt. You could use an index card taped other the dogs too.
Are you following Leah Day's recommendation to try leaving the feed dogs up to see if your tension is better? I know some do it that way. I lower mine. Though occassionally I have forgotten!