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I've been into mountain biking for many years and have done a good amount of carbon fiber cutting (handlebars, steerer tubes, seatpost,....)
The carbon fibers used to make tubes such as monopods are usually so strongely bonded together that you don't need to tape the part you want to cut. Fo example it is not like CF archery arrows where all the fibers will "open up" when you start cutting.
However, once cut, you will have to protecty the cutted part to avoid damaging the resin that bond the fibers together. For the side, electric tape will do just fine. If you plan to apply some weight on the cutted section, you could plug a rubber stopper inside the tubes.