As seen from inside the dome slit, starting at the lower right corner (actually I didn't have picture of this corner, so this is a reversed and rotated picture of the upper right), the cable wraps around a pulley. One strand is attached to a bracket attached to the shutter bottom corner.
The two strands go to the lower left corner and through a double pulley, then up. One strand (not the same one as before) is attached to a bracket attached to the left shutter at the bottom corner. The brackets were bent from standard 4" right-angle brackets from the hardware store. The attachment of the cable to the bracket has to be adjustable for fine-tuning, so I found a "lamp nipple" from the hardware store (essentially just a hollow threaded rod- "lamp nipples" are used to attach light sockets in household lamps, so they're hollow for wires to pass through) and matching nuts, and passed them through the bracket, wiht a nut on either side for adjustment, and then ran the cable through them, with a washer and a crimp-on cable stop on either side.
Both strands go up the side of the shutter slit. A spring and turnbuckle allow tension adjustment. The two small white plastic pulleys on the side are actually patio screen door rollers. Note the small pulleys are offset with washers on the shaft so the cable can be crossed between these pulleys and the next set:
