WHOA!
Before you modify the mast step because the side shrouds are loose, check that the mast is centered and that the mast rake is not excessive! In other word, you need to tune the rig before you modify anything permanently.
If the combined length of the forestay components is too long, there will be too much mast rake, which will make the side shrouds loose. (Rake is the term for leaning the mast aft. Different designs of rigs require different amounts of rake)
What does the forestay and furler drum look like? What does the luff ( front edge) of the headsail look like?
. The easiest way to measure rake by getting the boat level on the trailer, using a bubble level on the cockpit seats. Then hang a weight from the halyard using the halyard. At the height of the boom, measure the distance between the back face of the mast and the halyard. Also measure along the mast from the gooseneck to the halyard at the top of the mast.
Tell us the measurements. With a little trig, we can figure out wether your mast has a reasonable or excessive amount of rake.
A rig like yours would have between 0.5 to 1.5 degrees of rake, and probably on the lower end of the range. For a rough approximation, 1 degree would be 1:60 ratio.
I would guess that a boat with a main Sail like your boat would measurements roughly 19-20’ between the boom and the halyard exit at the top of the mast, so I would guess that you the plumb line should hang about 4” aft of the mast for about 1 degree of rake.
If there is significantly more rake than normal, you might have a problem with the forestay.
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Judy B
Retired sailmaker