cartridge mounting ? for clearaudio

a few kind of dummy questions here:
the clearaudio aurum classic that i have came with a bag of standard mounting screws, and was also attached to its box with a set of plastic mounting screws. are those just for the presentation of the package? or would one want to use those to mount the cartidge?

this cart. seems to be threaded, and does not need nuts to fasten it to the tonearm? should i be using nuts anyways to secure it?

along with the mounting hardward came a little metal plate, that would seem to go inbetween my cart and tonearm. is this to adjust overall mass? or change the height of the cart? i've never seen something like this before and there is no mention of it in my setup manual.
Don't use the plastic bolts, and don't use any nuts. And most important -- don't over-torque the mounting bolts. Just hand tight and then a tad more -- no muscle required.

As for the plate, it's for adding both mass and/or height to the cartridge. Mass if you are using a tonearm with a highish effective mass, height if you have a fat tonearm tube (like an SME V) which can touch the outside edge of some warped records at certain settings.

There's a great cartridge/tonearm effective mass matching table at:

I had similar concerns regd my clearaudio emotion. The manual is not particularly helpful.I set up the cartridge with and without the lead plate and was unable to discern any meaningful difference(could be my hearing!).
Nsgarch is absolutely right. Don't use the plastic screws. Have no idea what they are for.
Happy listening.