Manually manipulating the hammer after using the decocker would defeat the whole purpose of having a decocker.  DA/SA guns with a safety, hammer must be manually lowered all the way down.  DA/SA guns with a decocker are legal at the position the decocker lowers the hammer to.  This is reference to using these guns in SSP.  I have run into confusion at clubs where these guns aren't used much.  Mark