Now, the up-grades/improvements in audio is more a knowledge level on an specific regards than about money or high priced audio after market items.
I know that you already read this post:
https://forum.audiogon.com/discussions/picking-up-a-new-technics-sl1200g-tt-tomorrow/post?postid=159...
and what I posted is good for you too.
The best metal headshell for your tonearm are the magnesium ones that against what you already bougth are truly inexpensive.
In reality there is nothing new " below the sun ". The VTA/SRA characteristic in the headshell you own came from the very old times/vintage TT/tonearm manufacturer Dual that was ho invented the headshell with VTA mechanism.
Even my vintage MI cartridge AKG P-100LE comes with the VTA/SRA mechanism integrated in the cartridge body ! ! !
Btw, do it a favor and put in contact with nationalbar whom posted here about that 3M wrapp, that wrapp is a must to have.
R.