There are three possible design choices.
- Use lines that are independently cleated for both topping lift and foreguy
- Use a bungee for the topping lift
- Use a bungee for the foreguy
Of these choices, the first is common on large boats, but unnecessary for the DS.
On the latter two, there's a difference of opinion; I've made my choice, but I don't know whether there are any compelling arguments for or against it. It seems to work for me, but others report the same for their setup. The two solutions aren't equal, because the loads generated by the spinnaker aren't symmetric in the up/down direction.
The weight of the pole and the weight of the sail (in light airs) will push the pole down, while pressure in the sail will lift it. Therefore, to me, it seemed logical to use the static line as the foreguy, as it will not allow the pole to change angle when the wind increases. At the same time, the bungee only needs to be as strong as required to offset the weight of pole and sail. That seemed a reasonable approach, so I rigged the bungee as topping lift. As long as the bungee is strong enough to overcome the combined weight of sail and pole, this arrangement allows you to trim the pole precisely to any desired angle.
Others have rigged it the other way around. It would seem to me, that the effect would be that past a certain point the sail is allowed to rise on its own, with increased wind pressure, while stretching the bungee. (As a result, the pole cannot be trimmed to every angle, not unless the bungee is also adjustable). Perhaps that's a useful feature, but I haven't had anyone explain it to me in those terms. And it may be the case that this is of interest in different conditions than the ones I sail in. Because of local conditions, I find myself using the spinnaker most often in moderate to light winds, at the edge of its range of effective angles, that is, at a fairly broad reach, with the pole trimmed forward and down, sailing it almost like a gennaker.
I use a simple ring as fairlead for the foreguy, which works fine. The only mistake I made is to place it slightly off-center, with the effect that the foreguy tends to pull the pole away from the clew in some conditions. (So, wouldn't suggest to copy that part.) I cleat the foreguy on the cuddy top, actually, on the aft-facing edge of it. The bungee is attached to an eye-strap that's somewhere below the spreaders. Presumably about half-way between the ring and the forestay, but I'm not sure and do not have a way to do measurements. I strongly suspect that the precise placement isn't of supreme importance.
I experimented a bit until I came up with the right combination of bungee and line to give me a topping lift of desired elasticity and power. It needs to be able to stretch all the way to the lowest position the pole can be trimmed to, but you don't want it too soft around the horizontal position either. I know leave it attached to the mast permanently, and, when not in use, attach the free end with a shackle to the mast ring, from where I take it off to attach to the pole.
Unfortunately, I don't have the measurements for the location of the mast ring. I doubt it is 48" off the cuddy - that would be somewhere between 7 and 8 feet off the floor of the cockpit, and that's higher than I remember. I would suggest you sail with your setup, and if you find that you trim your pole at an upward angle a lot, then you could put a second ring in place to allow you to sail with your pole in the horizontal position. Under the conditions I sail, and given the particular sail I use for a spinnaker (which was not originally cut for a DS, although it seems to conform to class limits) I tend to have the opposite problem.