Novices and newbies discussion

Hello! I need some advice. I currently own a Holy Trainer v3 with the standard tube and a 45mm ring. It feels like it might be slightly too large, so I’m thinking about downsizing, but I also want to switch over to metal. I’m looking at getting a cage from AliExpress that has a 40mm tube along with a matching 40mm ring. Any thoughts or suggestions would be greatly appreciated! The linked community page Thank you!:)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)