Domain Mapping Slows Down Multisite

Hey guys,

I'm having some issues with the domain mapping plugin on all of my multi-site setups. For example on cu2.co.nz, it's setup on a VPS running a Multi site setup, iSecurity plugin and Wordfence (using caching) with some of WPMU Dev plugins for Buddypress, like Domain mapping for the sponsored websites on sub domains.

I've been working on it for several months now, using different configurations according to many online tutorials and help guides making sure my setup is super fast (all the known sources for speeding up Wordpress) and I come to this point where everything is still loading so slowly (loading pages and logging in) when accessing the websites (main and sub).

So I did a scan with P3 (Plugin Performance Profiler) and came back with these results:

Everything is running under a second, except for the Domain Mapping plugin that is taking up more then 2 or even 3 seconds to load. I have 4 multi sites using a VPS and all of them having the same issues with Domain Mapping.
And they all have way under 100 subsites running on it.

Any advice on this one?

Cheers,
Ronald