Scale Measurement Outside of Load Cells

Question

I'm building a scale. I cannot mount the load cells to the edge of the platform. The chassis are fixed to the floor and the load cells are fixed to the chasis. The platform is fixed to the load cells. 4 Load cells making a little square and the platform is a bigger square. So if you put a weight out of the load cell square, you read less values from the far load cells. Like in the picture;

Which formula gives me the real weight from 4 load cell value, where ever you put the weight?

Comments

What is the physics experiment/broader context this questions arises from?

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My first question and i guess i've just selected a wrong category without thinking. Sorry about that.

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Maybe "Applied Physics" would be a more appropriate category?
 

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I've changed it to that. Thank you.

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Voting to close as not graduate-level. PhysicsOverflow is a site for only graduate-level (and above) physics. PhysicsForums.com might be a more appopriate home for this question.