Self leveling over OSB

[Pete]

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

[nod]

Mapei  Eco will prime most timber 

I often straighten timber floors with flexible adhesive Then bed 6 mil cement board on top To give a perfectly flat surface 

Then drive screws in once set 

[Nickfromwales]

Mapei or Ultra. Both will do the job  

[Temp]

could you lift the osb and move the sound insulation if its just one spot?

[Pete]

16 minutes ago, Temp said:

could you lift the osb and move the sound insulation if its just one spot?

All glued down, be a real pain but thanks anyway