Hi Lizzy,
Thank you for your work !
Formatting it like
{{size|cm|height=379.5}} {{size|cm|width=453.5}} {{weight|kg|337}}
seems like the most logical course, if you're not sure all the units
for height/width will be the same.
Thats a great solution! Thanks!
Tangentially to that: for a while now I was playing with the idea of adding an extra parameter to {{size}}. For media like < https://commons.wikimedia.org/wiki/File:Confirmation_du_roi_Louis_VI_le_Gros..., I had dimensions for the piece of parchment and the seal. I was thinking of something like {{Size|unit=cm|diameter=9|part=seal}}. Would that be useful in your opinions ?