@Gippslander
Re your gov linkage photos and mods:
On my JKSON, there was much slop in the yoke as in your photo. I also made a bushing for the linkage & installed where you have the shim. As your, it worked very well.
In your photo, it appears that the yoke and rack are not parallel. I also had the same situation, which caused binding. The bellcrank can be carefully
bent to provide proper alignment.
Also tried the additional spring between the yoke and bellcrank, but noted no improvement, so deleted it.
Finally, the real secret (for my engine, and a few others, at least) was the governor spring as described in the WOK section of this forum. With all the gov linkage mods except the spring, I was able to get no load- max load Hz difference down to 4Hz. Replacing the oem gov spring resulted in no load-max load Hz difference down to 1Hz. the engine has maintained that small variation in RPM difference for several hundred hours of operation. There is very little RPM over-run or sag on abrupt loading of unloading.....about .5Hz
Cheers,
Hugh