Diamond Stays Pre-Tension On Leopard 42 Catamaran

[LifePart2]

My standing rigging is now 10 years old, so time to replace it before it falls down.

I am planning to replace it with Dynex Dux, which will be an interesting experiment. (See the various threads on synthetic standing rigging on all the major sailing forums)

However, the bit I am not clear on, is how much pretension do I need for the various shrouds and stays? How do I know how much to tighten both the diamond stays, and the upper and lower shrouds?

I have already looked at a whole bunch of forum threads and websites that discuss rigging tension, but none of them address the diamonds.

On our Leopard 42 we have the following:

Forestay/roller furling system (which will remain stainless steel)

Upper swept back shroud attached near top of the mast at same height as forestay.

One set of spreaders.

Lower swept back shroud attached just below the spreader.

TWO sets of diamond stays:

the outer one that starts a few feet below the upper shroud and ends at about boom height, and

an inner one that starts half way between the outer one and the spreader and ends about halfway between the boom and spreader.

Both diamond stays go over the same spreader (as there is only one spreader).

The mast has some significant pre-bend, and I note that there is a lot of tension on the diamonds.

The upper shrouds are fairly tight, The lower shrouds are relatively loose.

I am presuming that the uppers stop the mast falling over, the diamonds put in the pre-bend, thus stiffening the rig and, I presume, the lowers basically prevent too much mast bend when the main is sheeted in hard.

Anyone got any suggestions on how I would go about setting this all up?

I don't at present have a tension gauge? Do I need one. Would it work the same on dyneema and stainless rigging (since the flexibility of the two is different)?

Thanks

Noel