It sounds like you have the entire top frame. The larger hoop forms the rear edge of the roof. The smaller hoop mounts to the large hoop, angled towards the windshield, and forms the peak of the roof over the driver and passenger heads.
Former Owner of a 1981 Classic Roadsters Ltd. Duchess (VW)
2005 Intermeccanica Roadster
If you own a TDr and are not in the Registry, please go to https://tdreplica.com/forums/topic/mg-td-replica-registry/ and register (you need to copy and paste the link)