I was wondering if it's viable to use a flexible shaft on a CNC router to transfer the rotary motion from a stationary spindle motor to the head of the router. There are some flex shafts on mcmaster carr which have ball bearings and are rated for high load, but I am unsure if these would be strong enough for the large radial force applied to the end of the shaft when milling. Additionally, would they be able to transfer enough torque. Also, is there a good way to interface the end of the flex shaft with the collet on the spindle motor, which would likely be a er20 collet chuck, and to put another collet chuck on the operational end of the shaft. Also, how much longer than the maximum distance between the head and motor position would their have to be to prevent the shaft from bending at the head too much?