Dave, the old style wooden stock and tiller already wedge in by design unless a pin is stopping it from wedging in tight. Loose the pin, get a bungee.
Boris, the new Aluminium tiller has indeed a PVC strip that fits in a receptor cut out in the PVC insert of the rudder stock. The receptor groove does not run all the way to the back of the rudder stock but it stops at some point where it changes to the width of a a saw blade. The narrow part of the groove should prevent the tiller from moving back any furter at some point. When new it should wedge the tiller before the PVC block in the tiller reaches the end of the groove, if not it is time to replace the PVC block on the tiller for a slightly wider version. This is also a good moment to introduce a slight angle (1 – 3 degrees). The new block could be made from PVC again but hardwood may last longer (Please note that I haven’t tried hardwood myself yet).
Anyway, there are several solutions possible but I would consider only those solutions that guarantee a snug fit without any play. Usually that involves some kind of wedging mechanism. A pin most often prevents the tiller from tightly wedging in, and is often the cause of a wiggly tiller because it prevents the tiller wedging in deeper once it has worn a bit.
The same argument is true for the rudder bolt. It should be as tight as to prevent the rudder from wiggling in the rudder stock to get that all important feel in our tiller. On the other hand, the rudder should also come up easy when we want to beach our boat. There is a compromise here and it pays to adjust the nut precisely. In my case I have slightly damaged the thread of the bolt to prevent the nut from loosening itself. Once adjusted it stays in place most of the time. Others have used a second nut or locktight to secure it.
Then there are the pintels and gudgeons, they too should have no play but that is no problem with the new big black SeaSure blocks. It may be an issue with the old pintels and gudgeons that were made from sheet steel. The pintels often loosened from their crimp fit and we used to replace them with a long bolt and a nut if there wasn’t a welder around. Worse was the situation with the holes in the gudgeons, they got bigger due to wear and there wasn’t really a solution other then to replace them.
If you pay attention to all these details you end up with a tiller that tells you exactly what the boat and the wind are doing rather then having just a pole to steer the boat. If you didn’t see a header coming, a good tiller without play will tell you.