Hi Derek,
Here’s my opinion, free, and worth every penny of it.
The amount of slack in the leeward shrouds will depend more on how much you are bending your mast than on the original shroud tension. Mainly, you are trying to prevent athwartships bending of the spar under all conditions. Look up the spar when sailing. If the top is bending to leeward, you need more capshroud tension and vice versa. My own experience is that the lowers should be the tightest, the capshrouds second tightest and the intermediates, if you have them, should be just tight enough to keep the spar straight.
If you are using a lot of prebend, the lee shrouds will get very loose. If you are using near zero pre-bend as most of us do these days, then they will go a bit loose, but not as much so.
Al