Signing statement with master key?

[Cannon]

This is a hypothetical scenario.
Lets say if I have a keypair.
The master key is set to SC (signing and certification) which are the
default settings. The master key pair is only used on airgap with safe
data transfer between airgap and network connected computer.
Is it safe and possible to use the master key (not subkeys) to sign a
statement?

-- 

Cannon
PGP Fingerprint: 2BB5 15CD 66E7 4E28 45DC 6494 A5A2 2879 3F06 E832
Email: cannon at cannon-ciota.info
Bitmessage Address: BM-2cVaTbC8fJ5UDDaBBs4jPQoFNp1PfNhxqU
Ricochet-IM: ricochet:hfddt2csxnsb2mdq