I am a new owner of the 75 D pcr and have pondered the replacement of the guide rod. CZ sells the aluminum one and a spring, but read you need a round end spring to fit their aluminum one. I have not seen the polymer based guide rod being sold as a spare part anywhere. I do not plan to shoot it all that much, home defense and range activities. I would prefer to replace the plastic one with the aluminum one and get the right spring to fit it. OR get another polymer based one as a spare. Any suggestions other than the stainless steel one that cz does NOT suggest using in the aluminum alloy frame?