I'm tearing up carpet and putting down 3/4" solid hardwood, but have found that the subfloor is 3/4" particle board (yes, particle board, not OSB) on top of 1/2" plywood. From googling, I've learned this was common in the 70s-80s to bring a carpeted floor up to the same level as other tile flooring.

So, what to do?

I'm know the "right" thing would be to tear the particle board out and put down 1/2 or 3/4 ply. But that's a huge amount of additional work and cost.

I've read that some people will nail the hardwood down to the particle board, so I guess that's the other option. I was planning to use Primatech cleat nails, 2", which are barbed, and should go all the way through the 3/4 particle board, 1/2 ply, and 3/8" into the joists (which I'll try to hit, and will run the flooring perpendicular to).

I will only be in the house another ~4 years, so am not necessarily looking to do this the same way that I'd do this in a "forever" house. Existing wood flooring in the house is already pretty squeaky, so I'm willing to accept that potential bad outcome. I'm not worried about water wrecking the particle board. That said, I don't want to be the jerk who does it wrong and makes a mess for later.

If this was your project, what would you do?