I don’t use a 660 anymore, I’m using a 611 on a Shapeoko now. (mpcnc is now a lowrider) I reworked an existing vac adapter for the 611 to include a brush - the same brush I used with my 660 mount. The brush was rigidly attached to the vac adapter and the vac adapter was rigidly mounted to the 611. I had to make it to where the brush could float up and down and rotate a bit because whenever the machine made a 180° move on the xy plane, the brush bristles would actually lift the entire z axis! I never encountered this with the 660, but it may happen to some degree and flexible brush material might be worth a try.