Can I merge a grafts from an exported firewall backup into another?

[senseivita]

I want to merge the config of a firewall which was is being used only for a package into another one, I'd like to get the certificates from the former too so I exported it then gutted thousands of lines from it.

Can I merge it into another firewall?

I understand that when sections are imported it does a full replacement of the imported data but I assume the full backup must have a given minimum set of keys/tags in it since it's the only one that exports certificates.

If say, I gutted something (a full section) that's expected, will it be blanked in the receiver firewall or will it just ignore it?

I got: system, syslog, aliases (which should be already the same), cert, installedpackages, virtualip, ca and systcl.

The system section has quite a lot of settings but it's more or less the same in both firewalls so I think it'll be OK as long as I'm not supposed not to edit these files. :/

Thanks!