Re: INACCURACY POCKETING AND PROFILING CYLINDRICAL HOLES (instead of using drill)
Think of deflection not from the standpoint of the tool "bending" away from the material like you get cutting steel, but think of it as the soft material pushing away from the cutter then springing back once the cutter passes. We see this happen all the time cuttings soft plastics and nylon, especially if the part is thin.
I think your 900mm/m is too fast, but you said slowing down doesn't help. If your machine supports cutter comp, as Jim suggested above, this would be very beneficial for you in these cases. You could model your holes on size, then make the perfect fit through your controller.
If time is important to you, getting "precision" one-shot drills would make this a breeze. You don't need to spot or ream. Just drill (at crazy fast speeds) and the hole is round and on size. We do this in 4140 steel (a tool steel) all day long. It's a little scary at first because it seems ridiculous to drill that fast, but it works and the drills last a very long time.
Dan
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)