If you haven't already seen the Salvation Navy YouTube channel it's worth a look: https://www.youtube.com/channel/UCSYc21cjkfKE4vGmHc7SUmw
The guy who created and uploaded the videos is a cinematographer who restored an HA18. This is the specific video on mast hoops:
https://www.youtube.com/watch?v=vKkGt7ENRag
Marc Perry
Mount Hope Bay
Fall River, MA