that is a common problem. I've reinforced every I 20 rudder head I've ever owned to strengthen it and prevent that.

The springs are pretty standard - I wouldn't change much with that...however, the geometry is pretty complex on that rudder system and it's tricky to change/adjust. My Nacra Infusion (same rudder system) was bought second hand and the previous owner had carved out the lower casting where the roller engages...presumably to make it engage harder in the down position - they require a LOT of force to release and kick the rudders up.

If you are happy with the amount of force to lift/release the rudders and with the force required for a rudder to automatically release, I would only reinforce the top of the rudder.

I have some photos of my reinforcement method and will upload tonight.