Creative and cheap DIY turntable/tonearm tweaks

As you suggested,I went back and read one of your threads on tonearm tweaks which discussed adding lead fishing weights protruding from the vertical axis. I am not an audio expert but I did study college physics enought to make me wonder that such a small weight attached so close to the axis could have a measureable effect. Did you actually calculate the change in resistance to angular momentum that would result from this to determine its significance? It seems to me that a much longer outrigger arm would be needed such as a rigid wire attached perpendicular to the arm with the weights at the end. Inertia would increase in proportion to distance of weight from the pivot point.

My question concerning sand in the arm, which you said was "out of the question" would also increase the inertia of the arm and with proper counter weighting, would be indistinguishable, in terms of the physics, from your outrigger,in the horizontal dimension. It would also increase inertia in the vertical direction. (But there may be other reasons why sand in the arm is a bad idea).
It seems to me more physics is need here. It is interesting to hear that someone is "blow away" by a tweak but the audio press is full of too much of this hype to give it credibility without solid analytical justification.

As I understand it, compliance is how much a cantilever bends in response to the weight of the cartridge. I was not proposing to change the weight, just the mass. Mass and weight are very different things. With counterbalance a cartridge can exhibit no weight but be quite massive.

Ah, Ok so you are (both) saying that the cantilever needs to move in the vertical plane as well as horizontal for music reproduction (or is it just because the record is imperfect and potentially warped?)? I had thought that stereo reproduction only depended on horizontal movement and that the record grooves were flat in the vertical plane (except for that expirement back in the 70's with Quadraphonic). Certainly you are right that if a cantilever must go up and down in response to the grooves, more mass would be damaging to the record. If, however, it only moves horizontally, more mass (not more weight, just mass) would not damage the grooves.