Hi Klaus,

what I have observed is that our rigs move about a lot as we sail trough waves. The thinking is to reduce weight aloft to get less inertia from the rig movements and thus get more speed.
The opposite value is increased drag if synthetic materials have a bigger diameter than metal wire.
Are you able to quantify this in a meaningful way? How much will total drag increase if going from 3mm to 5mm stays. The "reduced inertia" factor can be calculated, but how to compare this... I have no clue but I have a feeling

Additional advantage could be easier righting for lightweight crews and a small degree of better righting movement.

I dont see why the jib makes a difference in metal vs synthetic rigging? Unless the rigging is really stretching and flexible the forestay will be tightened by the mainsail sheeting loads going upwind.

What is the issue with water and UV on carbon? Is carbon fibers UV degradable? Water degradable? Or are you thinking of the fittings and resins being broken down by UV and galvanic corrosion?