Cartridge for stock Technics 1200G tonearm

No problem, but 12cu is not the lowest compliance and normally low compliance cartridges are also too heavy for stock headshell to balance it. For example my low compliance Argent MC500HS is 8cu (7gr weigh) and it was impossible to use with most of the headshells.  

Anyway here is the article about it http://www.ortofon.com/support/support-hifi/resonance-frequency

It’s important to know cartridge compliance measured at 10Hz (not at 100Hz). If the compliance measured at100Hz (it must be stated in the cartridge manual) then multiply it on 1.7 to transfer it to 10Hz compliance. Then anyone is free to calculate resonance frequency. I do that with my Cardas LP.

High compliance cartridges (30-40cu) are lightweigh ones, you may need silicone fluid damper to use it not Technics tonearm which is not optimal for high compliance cartridges.

So it’s "safe" to use Mid Compliance carts with stock shell on this tonearm, that’s pretty easy.

I am going to listen to Ortofon cadenza bronze.  I will let you know how it sounded

I am going to listen to Ortofon cadenza bronze.  I will let you know how it sounded.  I agree the stock headshell seems to be the one that works with this table

Audio Technica ART 9 or Dynavector 17D3?  Which would be the best match ?

I'm using a Soundsmith MIMC* on my 1200g and find it to be a good match with an LP gear Zupreme  headshell. First rate sound in all parameters.