We have done fleece backing on our Gammill with no problem

Love the fleece and Minkee on the backs of quilts. Just make sure that you don't stretch the backing. Works great with my APQS machine.

i've used fleece on the backs of many quilts - quilted on the long arm-
they stitch up beautifully!
the one thing to keep in mind is the stretch of the fleece- one way stretches more than the other- figure out which way is which-
and do not stretch it as you roll it up-simply smooth it.
i've done them with batting- without batting- with pieced fleece/minkie
just becareful of the stretch- use a larger needle- longer stitch length- and have fun with it- the kids in my family request fleece backed quilts all the time- they are called the 'get-naked' blankets! they love to wrap in them after their showers :)