I fmq on 3 different machines and put the pedal to the metal when I fmq on all of them. I've found it's easier to control the speed I'm pushing the fabric along, then to control the speed of the needle. If I want a smaller stitch, I push the fabric slowly. If I want a bigger stitch, I push the fabric faster. When I feel like I'm getting out of synch, I just stop for a moment to recoup. The thing to remember is you have to be consistent on the speed you are pushing the fabric along on the project you are working on so your stitches will be consistent. I never get loops on the underside when I do it this way.