As the title says, in an asymmetric scenario, is it possible to restrict CQB spawns to just buildings that are being used as installations rather than the whole settlement?

Have you tried choosing 'Tactical' over 'Civilian'?

Other than that there's no way to reduce the CQB unless you make a specific taor marker really tiny, then you'd need to know which building was being used for the asymmetric installations...

Are you wanting the insurgent installation to be better defended?

Haven't been able to play Arma for a while but tried this recently and seems to have worked thanks :)