Well, I guess I did mention finishing the second patch last week.
If you have soft spots, putting in a few braces underneath is a no-brainer. If the wood got wet, and it has deteriorated at all making it soft, remember you can mix up a thin mix of oil based paint or shellac and work it into the wood. Yes, you can use rustoleum, even though it’s wood, but you want to cut it about 2/3 mineral spirits to 1/3 paint. It will soak in everywhere and when the mineral spirits flash off it’ll stiffen the wood fibers.
Thanks, I'll try to keep that in mind for future projects (or parts of this one). I think what I've got left in this area is more like sagging, not soft and moving like the previous two spots. Maybe where it got wet in the past and dried back out.
I am rather sensitive to variations in the surface I'm walking on, atleast when it's supposed to be a flat surface. I can even feel the roughly 1/32 variation between the patches and old flooring, and that is through my shoe soles and the carpet squares I have laid over it. I think what I'm noticing in these other spots is more the variations in level, than actual soft spot.
Going to get the braces, then the felt to shim up some before laying the thin ply over everything. Also going to completely cover the subfloor with the felt before laying down the thin ply, it'll serve to eliminate squeeking and act as a little bit of a barrier. Between the thin ply, the padded underlayment, and the flooring I put down, it should remove or mask any variations in the sub floor. I do still need to figure out the right way, or at least the most practical way, to attach that thin ply to the sub floor.
To think I almost tried to use 23/32 instead of 19/32 that matches the existing flooring, it would have been sticking up 1/16" or better. I probably could have feathered it out with sanding and leveling compound, then masked the rest with the stuff mentioned above, but I probably still would have noticed the high spot when walking through. It would have driven me up a wall.