Absorbent Open Ceiling

If it were in fact such a slight protrusion the OP could almost just install the rock directly to the underside and that would work. But as you and I know, nails come from everywhere for many a purpose...walls, multiple layers of sub flooring, etc, so I would have a difficult time (based on what I have seen) that this would be a uniform pattern from one bay to the next. And some folks have argued over if they can or cannot just cut the nails off...and the answer (if it comes up) is no, can't or rather shouldn't do that. But, sure, if a person wanted to place caulk in-between the two materials, it wouldn't hurt a thing as long as the protrusion of the nails is really, really minimal.

xSpace wrote:

nails come from everywhere for many a purpose...walls, multiple layers of sub flooring, etc, so I would have a difficult time (based on what I have seen) that this would be a uniform pattern from one bay to the next.

At this point, they actually are pretty uniform. A good portion of the subfloor doesn't have any nail points coming through at all. But the ones that do are all about the same, < 2mm There were about a dozen larger, different type of nails that penetrated deeper, but I had already cut them off before reading your further advice : ( ...oh well. I finally got started on this and I must say - It's kind of a pain in the arse doing it with the cleat method. I'm a one man operation over here and holding drywall while trying to hammer finishing nails is not fun at all. I've read some of the forum debates over cleats vs screwing directly into the subfloor and I don't remember there being an agreement about which method worked better and by how much. But after hanging a couple strips of drywall with the cleats, I'm really tempted to resume the task tomorrow using the subfloor screw method and finish the job that way. Thoughts?

The finish nails are to support the material until you can actually install the cleat....so hell yes...get a screw gun and some screws and make it easy on yourself :)