I didn't say my description was the answer to the loose headset, just to have you better understand what was in front of you.

Forks can have a molded/machined in seat for the cartridge bearing to center on, or not have one. Not having an integral seat is the classic way (and using a precision cutter to establish the factory seat's dimensions so a separate crown race seat ring can be pressed on is a many decades way to prepare the crown for the bearing). But with the entry of carbon and it's not liking being machined (cut) (for a few reasons) a different way has come about to allow the lower bearing to properly be centered and square to the steerer. This way is either a split separate ring, as is shown on the left. Or it's to have the fork manufacturer mold a seat during the fork's construction.

So the question for you is does your fork have a lower bearing seat on it? Is so then the imaged LH ring isn't needed, regardless of it's size. If not then you need to get the proper size ring. Said seat/ring also needs to be compatible with the cartridge's bearing design. Specifically the bearing's angle of contact surface (typically either 36* or 45*).

I take it that how ever you got the frameset it didn't come with the proper headset? That it had no info about what is the correct headset? If you got the frame from a LBS shame on them for not being able to help you out. If you got the frame from an on line source then also shame on them. If you got it from a privet person still shame on them. Any way you are experiencing the cost of dealing with this frame. Finding info has it's cost too. I am not familiar enough with your specific frame and fork to give you exact/specific answers. Only experienced enough to help you understand what you have and what you need to do next. Good luck. Andy