Hi Captain,
Thanks for your post. Using composition in your case is correct, and derive relationship does not fit into your case. According to SysML Specification v1.1:
“A DeriveReqt relationship is a dependency between two requirements in which a client requirement can be derived from
the supplier requirement.”
Attached you can see a sample of derived requirement which I picked from SysML Specification v1.1. Hope this helps.
Best regards,
Lilian Wong 
sample_from_SynML_Spec.png
