What nails for fixing down a large floor

I am looking at a Gym floor, which has an excessive amount of squeaking.

I have had a look underneath, and my best guess is that the floor was never nailed down (maybe glued).

The boards are 60mm by 19mm Spotted Gum (I think photo to follow). The hardwood joists are at around 420 centres.

The floor is getting sanded and polished, and I am thinking that to limit the squeaking I could:

1) Shim the 720 points where joists meet bearers?

2) Run a bead of glue underneath the floor on either side of each joist?

3) Top nail by hand 65mm bullet head nails, then punch and putty each of the 16,000 holes. (one per board) plus predrilling.

4) Machine nail with T-Head type brads/nails the 16,000 holes then punch and putty.

My questions are:

I assume 1) will minimise a small amount of the noise but not the bulk of it.

I guess 2) wont achieve much

3) is probably the way most guaranteed to work

4) is probably the cheaper option of the last two

And finally is it common practice to lay a gym floor without nailing it? Is there an assumption that the weight of the floor will hold it down?

Cheers
and TIA


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