Going to be installing 3/4" T&G CDX ply over a slab soon (with poly underneath). I use tapcons to fasten the ply to the slab. The room is probably about 250 sqft.

I've done this before and If I remember, i think i used like 12 fasteners per sheet of ply (4 on each edge and 4 in the field). Does that seem right? When I was done, I remember thinking that it might have been overkill, especially considering that the Ply was T&G. Pre-drilling and sinking all of those tapcons is time consuming, so if I can cut back on the number without risking anything I'd sure like to.

Just for the sake of mentioning it, i'll be installing 3/8" pre-finished oak over the ply later on. Have already through this in a couple rooms, now it's time to do the Den.

Any thoughts?

Why T&G? I know it's used in some regions but fastened to concrete? I've never seen it. There's always been debates on this subject. I recall some job specs calling for 32! One per square foot. Imagine doing that on 2,000 SF

Most of those nightmarish plywood jobs I handled in the past were more like 24 per sheet. To keep things in check it would be nice to know what you did before as you could get a sound and feel underfoot difference, but you're probably going to be the only one to notice it.

12 does sound weak, but...