When connecting the tillers to connecting bar - it didn't work... So it had to be modified a bit. What I did here was that I cut the tiller end to angle, make it 90 degrees with rudder gudgeons:
Another Hobby Kat builder, Francis from Malta, had a different solution, like this:
Francis also has an interesting solution on rudder sinking issue - he stretches it down with a line with a bungee cord attached to the end...