I tried a few simple ideas on a 75 arm and achieved a much improved sound.  This was done using anything at hand so think of these images as functional bodging.

First - a splint for the counterweight.  Made from an old dust bug stand and some twist ties.  As soon as I did this I realised that the plastic-chrome shroud could not be refitted, so that was left off.

Next was some way of supporting the knife edge inserts.  I tried various slotted screw heads and decided on these.

They fitted the holes already there to locate the v-blocks.  It was a nuisance keep threading the arm wires through the hole in the arm pillar so they trail out the back of the arm to the junction on the plinth.  This allows the arm to be lifted off complete, maybe even use interchangeable arms.

There's no way this bodge should have worked but it did.  Sound improvement means the music is clearer, pure and simple.

Mark2

With the second arm I tried to improve the rigidity across the join.  The curved section bar fits the shape of the arm more closely.   

The cable ties are easy to use, and clamp the splint more effectively than twist ties.  There is still some side to side movement, but this improves on the mark1.

Then I thought about alternative supports for the knife-edges, what about a tube?

Worth a try.  The knife-edges can move around inside the tubes, but the arm is stable while playing a disc.  Sound is now different, more testing to do.