Have you tried using a slightly larger tension screw? This would be an easy fix for the tension screw holding the rudder to the rudder assembly. If you're wanting the full assembly, the i11 uses the following:
RUDDER ASSY W/SM BLADE - TWIST
I've tried "slightly larger" screw as you've suggested before, and it wouldn't fit. This is for the screw holding one of the steering lines to the rudder. Would help if you give me an exact size, or better yet have one in stock I can purchase. The tension screw in question stripped out the very first time I did a rudder adjustment, no cross-threading involved. It's good enough to serve as a post for tying off the spectra, but with the wire kit you need solid tension to keep the wire in place.
As for replacing the entire rudder assembly, my i11s is still under warranty and I'm in contact with a local dealer to have it replaced. However, the dealer that sold me the kayak knows nothing about my boat, or it seems to me Hobies in general. Had a terrible experience with them and not going back.
The dealer I'm talking to now is extremely helpful, but they are also a "new" dealer and I was wondering if there are unlisted instructional videos on DIY rudder replacement for the i-series I can consult (like your video on upgrading steering wire), so I can ascertain if replacing the rudder assembly is within my capability or not. If not, I'll go to the new dealer and hope for the best.
Hope that makes sense.