AR GameObject Position for all clients

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I am trying to spawn a bomb from a player in my multiplayer game in AR. The reason I mention this is because when I place my AR arena it's in one position but the other player may place theirs somewhere else and the arena positions are different.

The bomb does not have a photon view on it so when I press the bomb button I have, I send an RPC with the bombs position to all clients. Then I subtract the arena position that was placed from the sent bomb position and spawn the bomb across all clients. I am doing something wrong because the bomb is not in the correct position on any of the clients when it spawns. Is there a certain formula for this that I am missing? I feel like there needs to be a relative or shared point I need to compare to.

Thanks for any info!