Non Rotational Black Hole Merger strain, with only nuclear oscillation effects.

Surprise !!

If Black Holes have no inertial mass, due to their non Baryonic Dark Matter Axion/Higgs content, then no rotational strain but only nuclear particle tension effects will take place during merging.

see also:  https://www.researchgate.net/publication/324497489_Dark_Matter_Black_Hole_Galaxy_Hierarchy_according_to_Quantum_FFF_Theory 

Black Hole merging without rotation, due to massless BH Inertia absence, according to Quantum FFF Theory. (duration about 1 sec.) 
Neutron stars however have normal baryonic mass and consequently rotational based strain effects. (duration about 30 sec ) see below.