Jonathan, Adding a cleat which is not permitted within the Class Rules would certainly infringe the Class Rules, however it was attached. I expect that what you can see in the photo is two clips clipping together to make the shockcord into a loop, as is specifically permitted. You can see the tale of a knot dangling.
It is not so obvious in this scale of photograph, but if you click on the photograph to display it in a separate window it would appear that a new cleat has been fitted under the boom between the kicker and mainsheet block loops.
If fitting that cleat has involved drilling or other permanent fixing then I suspect this is outside of class rules.
CA Technical committee have final say on that aspect, of course.
Shockcord is permitted to retract or reduce slack in ropes when released/uncleated, with limitations; - must be maximum diameter 6mm - can have optional attachment hook/s - shockcord and/or hook may not change the function or performance of any fitting or rope - must not pass through or attach to any sail cringle.
Personally I don't bother with that schockcord, but sailors who are often in light winds or on sheltered small lakes may have a greater need. Points to note; - The looseness in the clew strap allows a good degree of outhaul ease movement before the webbing even needs to slide on the boom - The outhaul will ease more easily when the sail is under more pressure upwind, rather than downwind (so ease it just before you bear away, rather than after) - You will find the clew strap slides more easily on the boom with less kicker (vang) tension
If it is elastic it is in my book class legal and I have senn boats at the European passing the measurement checks with such elastic. It is only helpful for low wind conditions,
