Need help with rudder/tiller issues.

My 2003 H16 has some rudder issues and I need some advice/help.
I have re-bushed the gudgeons and they sure needed it. That made tacking easier/possible!
The problem is getting the rudders down and keeping them down.
On one side the rudder is easily locked down but it needs more spring tension - however the delrin screw simply refuses to turn. I will remove it by drilling it out. I have the drills and the 3/4" UNC tap for cleaning the threads up.
On the other side I found that the plunger was not pushing all the way up, no matter how tight I wound in the delrin screw. I pulled the delrin screw and spring out but the plunger would not come out, either the top or the bottom. I had to drive the plunger out from below to remove it. I have watched videos where someone removed the cam and the plunger goes flying! There is no way the plungers I have would do this, without removing metal from the inside of the casting. I then took the cam off the other side, expecting to see the plunger go flying- but it won't come out either. I now believe that the plungers on both rudders do not protrude far enough to put sufficient pressure on the cams. I have ordered the parts to replace everything and I will be interested to see how easily new plungers can be fitted, or not.
Anyone else had this issue?
In addition the tiller arm (only on one side) is too tight on the rudder stock to allow me to easily drop the tiller bar in the locking down process. On measuring both tiller handle castings and both rudders I found that the casting on the problem tiller arm was about 1.5mm smaller. Both rudders are 25.9mm thick and the opening in one tiller casting is 26.71mm and the other is 25.44mm. The castings don't appear to be damaged at all and I wonder if anyone else had found this.
Should I remove the 1mm or so off the casting? Is this common?

Plungers can stick, that's for sure, most times just some silicone spray will get them moving. I have seen the plungers so worn out that they bind in the bore so new parts are a good idea. While you have it all apart, you should clean the plunger bores out with a nylon brush, a round one if you can, like a gun cleaning brush, along with some soap and water or brake cleaner spray. Then when installing and test fitting parts, use some silicone spray (Dry spray if you can get it) and coat all the parts when you put it back together. Are you installing new cams too? That will make it easier to clean and then test fit the plungers.
As far as your tiller casting, I just measured two new/never installed casting, and they are both at 25.5mm, my epo2 rudders are 22.7mm and my girlfriends older rudders are 21.8mm. If it's only 1mm you need, you could bend the casting out a little further where it bolts on rather than grinding away material. Most times people are installing shims to fill a gap between the rudder and casting. It makes me think someone used a SS nut and tightened it too much, most boats have the nylon nuts. Again, how often to you spray lube the parts, I carry a can in my parts box and spray things up every 2 or 3 of trips to the water.

_________________
Buxton
18' T16 Silent Lightning (16' T2 Hybrid)
11' H16 White Lightning
79' H16 Green Lightning

Thanks mate!
I have had a really good look at it today.
The plungers were really dry and both had to be hammered out.
One of the delrin screws needed to be drilled out. Having the 3/4"UNC tap made the process easier.
When its all cleaned up the new spring and plunger work perfectly!
When assembled back on the boat they worked brilliantly.
So the only drama was the one tiller casting binding on the rudder. I ended up grinding about 1mm from the inside of the casting.
Now that problem is fixed I have realised that the pivot bolts need to be firm but not tight to allow the system to work.
I am learning so much.