Finally, after 2 weeks of letting the sealant dry, we got into riveting the trailing edge of the rudder. The trailing edge ended up being nicely straight.
Afterwards, we got into rolling the leading edge of the rudder. This ended up taking a while, but we got a nice curved surface.
Unfortunately, a cleko teared a little bit through one of the holes in the leading edge of the rudder. So, I need to follow up with Vans about this.