Specifying callbacks for behaviours extending gen_server

I am designing a behaviour that extends gen_server and thus I want all of gen_server's callback specification in addition to some additional ones on top as part of the extension.  In the past I have favored using the `-callback` attribute as recommended in the documentation but then I saw someone recommend the following when extending gen_server

> behaviour_info(Type) -> gen_server:behaviour_info(Type).

I tried combining the two approaches but such is not allowed (which makes sense).  I believe my options are to append my callbacks to gen_server's list using `behaviour_info` or to copy gen_server's callback specifications from the OTP source.  Copy-pasting code just feels wrong...  how bad is it to use `behaviour_info` over `-callback`?  And am I taking the right approach?

Thanks,
Brett