A photo of your boom and fittings would clarify things,
but from what you say you already have enough pulleys. As you only need one pulley per reefing line.
the fixed end of the reefing line is simply secured to an additional mainsheet slider (i.e. the fitting that sits in the track on the underside of the boom). This has the advantage that you can fine tune the position (without drilling holes). In fact I have seen the pulley secured to this as well on a short lanyard – so you don’t need to drill any holes.
Of course you will need a second cleat on the boom somewhere near to the gooseneck