I got some rudder info from a fellow Helms 25 owner awhile ago
Here are pixs of my original above water rudder section.
The rudder on the Helms is rather larger. I have a feeling it's design is part of what makes the boat track so well and have great balance. A smaller rudder with a true foil designed for the boat might produce the same results, but you would have to look into that.
I've never seen the winch relocated. But there is plenty of room under there to design something. I really think its location is not that bad. If it were out in the cockpit the exposure to saltwater would result in a rusty mess. You do not need to sail with the centerboard all the way down. In fact, it's best not to. From what I've been told, your only suppose to lower the centerboard enough to balance the boat. I lower mine until the tiller is neutral, little or no weather helm. It takes 30 turns of my winch handle to fully let down the centerboard. I usually end up 8 to 12 turns depending on wind and sailing conditions and leave it there for the rest of my sailing that day. 10 to 12 turns is less than a 45 degree angle for the centerboard and just about the same or a little more than the depth of the rudder. Like this
Here are some pics of the lower section on the trailer
I hope this helps. let us know if you have any other questions.