flying outside the triangle
With an assym, I assume you want to fly it outside the foretriangle so that necessitates mounting any block above the forestay. I used a stout eyestrap to which I attached a block and shackle, through which I rove a 5/16" line, added a snap shackle to attach the head of the assym to, then brought the halyard around a new cheek block at the base of the mast, and back to a new cleat at the back of the cabin bulkhead. At the stemhead, you will need to attach the tack of the assym to a point forward of the forestay. The big changes will be at the aft end of the cockpit where you will have to add turning blocks and cleats for the sheets.It may cost a couple of hundred $ to rig it, but the first day, when you have very little wind, and decide to fly your new kite, it will all be worth it. You will notice that you are sailing along at the same speed as if there was adequate wind for a jib.If on the other hand the assym is small enough to fly (and tack) within the foretriangle, then you can get away with using the jib halyard, although, like you I have a furler, and mounted my halyard block just under the masthead mounted forestay.