Hello Grain
A few points from my own experience and thoughts on future plans.
We have some engineered oak flooring that sounds just like what you describe; in this case it is a big expanse on a Ist floor suspended floor (in an old chapel) and the boards are 300mm wide. It looks fabulous and seems to wear well.
The construction is 6mm top layer of oak, core of mdf/hdf whatever and a very thin balancing veneer underneath. From memory we had the boards delivered unfinished and finished them with Osmo Hardwax.
They were installed on a 22mm chipboard substrate, covered with a 6mm plywood layer screwed down and the boards were then glued down with a flooring adhesive. This appears to have performed well. A few offcuts of boards that I have lying around (in a damp garage) have warped dramatically, no doubt due to the differential movement in the 6mm oak and the paper thin balancing veneer. If I look at our floor, I think there is some small tendency to crowning of the boards, but not really an issue or noticeable as this is kept more stable and is of course glued down all over.
For the above reason, I would be wary of relying on just nailing through the tongues etc as I would be concerned about crowning/cupping of the boards. I would definitely look carefully at any very thin balancing veneer.
I am looking for some engineered oak flooring for our dining room and sitting room and intend to get something plywood based with a more substantial balancing veneer. In that case, I have already installed Rockwool insulation in the floors (again on a Ist floor), primarily for sound insulation.
The fixing method I propose to use is this system
http://www.epms-supplies.co.uk/admin/pr ... System.pdf which should provide good sound deadening with the underlay mat. It does of course need to be laid on a substrate, so might not be ideal if you have height issues (although perhaps you would not need 22mm thick flooring.
Anyway, just a few points from my own experience etc.
Cheers
