I am installing 3/4" red oak over 23/32 ply. In one of the posts it was recommended that 2" 6D 15 gauge nail be used to face nail where necessary. The total thickness of HDW and Ply is 1 1/2' why use a 2" nail"? wont this imped setting the nail below the face?

I use 1¼" and if I remember to mark the joist, I will stick a 2" in every joist.

Thanks Floorguy,
I am installing over a slab, so no joists. I assume the nail will bend under the ply if it is too long.. therefore no harm done. It that right?