About the strenght of the rudders: honnestly, I don't know. They are reinforced with bras tube, hope it works. Worst case scenario, I made a mall of them, so if one is lost, I can reproduce it.
For water comming in, I don't think so, since the rod sits in another one, just bigger, with no space between them. If greased, it won't let water come in. Better grease it every ten or so runs. And still, if water comes in, I made a watertight bulkhead at 9 cm from the stern (were the strenghtening is in the Revell hull). That'll have to do the job of keaping water out.
If all that fails, I'll have to install a small pump (costs about 10? I think..) But I don't think we'll need that.
Me and the owner, a fellow student, are in exams now, so we won't be workng on the Herman for a while. As soon as we made some progress, I'll post it here.
Greetz, Johan