Custom settings MTU and MSS override

[Antibiotic]

Hello , have a test and found optimal MTU and MSS for my client. The question is, where to put this figures " –tun-mtu 1470; –mssfix 1430; " above all or down all or does not matter? Please advise:

Is it possible to set this on OpenVPN interface or better in custom options?

[Antibiotic]

@Antibiotic Idk , tried to set in custom options:
tun-mtu 1470 but when restart OpenVPN client going msg:
OPTIONS IMPORT: tun-mtu set to 1500

Please, how to override MTU properly?