Robin,
I cut both glass fiber reinforced laminate and some with carbon.
I’m not too worried about the carbon dust as I keep the vacuum running, close to the cutter the whole time. I just don’t get that much carbon dust floating about. I haven’t felt the need for a water bath.
I use a 1/16 inch,single flute, upcut bit, with a plunge of only 1mm per pass, standard speed that is shown in the EstlCAM documentation. I use a Dewalt 660 so I only have the 29000 RPM for the bit.
Try a shallower cut first and make sure the EstlCAM tool description has the same diameter as the installed bit. I would think that an incorrect diameter is possibly the cause for the incorrect dimensions.
Another reason for the cutting difficulty is that the resin used in the carbon laminate may be much harder than that used in the glass one.
Mike B.