I think that it is important to think about the answer to
@Jraef 's question, because I don't think his point was that you _shouldn't_ send in the RFI because of the risk, but rather that you should evaluate _why_ you might want to take the risk.
Will it put money in your pocket? Enhance your reputation for saving your employer money? Protect the environment by saving on un-needed materials? Make you feel good because you aren't wasting? Answer what is your motive and then decide if it is worth the risk. It might very well be.
Additional points:
You are talking about $25K of wire, but in a job where $25K is a small fraction of the total (1/9 of the wire cost, plus all the raceways, labor....). Does 8 vs 9 sets make a differences in any of the other equipment (conductor termination points, conduit layout, such that 9 sets might be cheaper to install even though the wire is more expensive?
What assumptions did you use in your voltage drop calculation? Not just current, but power factor, conduit type, and conductor temperature. While I expect the voltage drop to be acceptable with real values for those aspects of the install, if I pick the worst case combination (75C conductor temperature, steel conduit, PF 1, 3000A) then voltage drop (according to the southwire calculator) comes to 3.04%; maybe that worst case calculation is what drove 9 sets rather than 8.
