Hello Everyone! I am looking for some advice on best practices for installing engineered hardwood (7.5" wide, 3/4"thick) on what appears to be a 12" wide plank subfloor.

I recently pulled up some boards to see what subfloor we were dealing with on an upcoming project to find wide plank (~1" thick x 12" wide) subfloor. Installation instructions on my floors indicate they should not be installed over plank style subflooring. The wood appears to be in good condition so I think my plan is going to be secure the subfloor planks with additional screws, then put down some plywood on top of it (glue assist + screw), then put own the floors (glue assist + nail/screw). I am looking for any advice on what material and thickness of plywood to use in this case. Is OSB OK or should I avoid? Since I have the 1" plank subfloor can I opt for a thinner plywood?

Any and all advice is much appreciated!

Why? It's done all the time, providing the subfloor is flat and sound.