Double spreader, swept vs straight?

[rpack]

Thanks Rob,
That leads to the next question: Single or double spreader? I can move my old spreaders and brackets over to the new mast, and move stays, hounds etc, but wouldn't double spreaders result in a stronger rig? And how to figure spreader length and sweep? I can draw the deck and rig in cad and figure out how to connect the dots from the stay attach points to the existing chainplates but that may not give me the optimum angles for the wires at the mast.