Ok, yesterday we've been testing some different set ups with different types of rollers. The conclusion in the end was that it doesn't make any difference for the force needed to kick up the rudders. It only makes a difference for the space for motion when they are fixed in the down position. In the end we've made it original (found a drawing on the web) with rollers we appeared to have in our box :-)

Nevertheless I think it's at least remarkeble that when you fix the rudders to the boat it is not possible to release the rudders when putting force on the top of the blades. We have put quit a bit force on it, but they didn't release. We also were afraid to put more force on them, so they would break again.

After that conclusion we decided to spend our time wisely and started repairing the broken rudders, so we will have some spares (which are reinforced)

If nobody has the experience that these rudders should kick up easily when putting force on the blades, we have to accept that apparently it works this way....