Hi - there does not seem to be a perfect approach to this - at least that we’re aware of. At dahai.uk we write the IPFS uri into the note field of the asset when it is created like this: ipfs://gsdfgsdfsdfgsdfgdfgsdfwhatever/
We then take a 32 byte hash of this string and put that into the metadata hash field. Whilst it is possible to change the note field, the hash ensures that the holder knows if it has been modified.
Not a perfect approach, and would love to hear of alternatives.