Might I also offer making the construct invisible and using bb's envirosphere? If you go through the tutorial you can regulate lighting within the sphere and it has some great additions BUT you will want to create a ground plane with a transparency map to blend at the edges and use ground textures close to your HDRI since unfortunately SF does not use shadow catchers. And a Possible Shaddow Catcher work around here

Boni

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"Be Hero to Yourself" -- Peter Tork