The .084 that comes stock is unusable, IMO. I went to a .095 from there, but it was still too floppy for me. The lightest low E I've been happy with on my VI is a LaBella .102. You can order custom Bass VI sets from them for relatively low cost.
As for the rattle, it's a matter of tweaking the action/truss rod until it goes away. Unfortunately, that's the best advice I can offer you.
My main complaint with my VI is the bridge/saddle setup. It's definitely the weak point on the instrument. Been thinking of going to a StayTrem or Mastery bridge, but other projects are higher on the priority scale at the moment.
Precision + Streamliner + Bassic 15 (GBD Club #103) = sonic bliss