I'm using this registry with regctl[0] to chunk uploads (to circumvent 100MB limit), works just fine for huge layers with models.
With regctl you will also get 'mount' query parameter for upload initialization with the proper blob name so you can skip additional R2 copy when multi-part upload finalisation which speeds up the upload (and avoids crashes on larger blobs).
This is not part of docker registry API, so I never got to PR that.
[0] https://github.com/regclient/regclient