My kitchen subfloor is 1x boards over 2x8 joists and the rooms next to it are 3/4" hardwood. To make up the difference should I go with 1 layer 3/4" a-c underlayment ply wood or two layers 1/4 sureply over 1/2 exterior grade ply with lower quality face. I am concerned about flex in the floor and fasteners showing through. I could screw down the 1/2 and then staple the 1/4" over it. Or just staple down 3/4". I would prefer not to use adhesive on the subfloor as it would be difficult to pull up later. Right now there is particle board over the subfloor that is swelling in places has to go.