When the floor cassettes were installed in my timber frame, some of the sound insulation got trapped between the joists and osb floor and created an uneven floor. I need to level this floor out before I lay my engineered oak floor. This uneven area is only in one corner so should make it relatively easy to flatten. I also need to overlay the OSB with 9mm plywood to overcome tiling heights in the bathroom and thus propose to take the plywood as far as I can and then use a SLC to level the area which is very uneven. I have some Mapei Primer G but not sure this can be used to prime OSB and I tried to ring Mapei today but they are not answering calls due to Covid. Can I use SBR or does anybody know a good primer for OSB? Once I have primed I will also put some screws into the OSB to give some extra grip for the leveling compound.TIA