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I am not an engineer, so have just a laic explanation, but could it not add some sturdiness, help splitting the clamping force on a bigger area? Maybe just a countersink with a washer? As said before it would be on the steel dropout on the inside and on the other side a recessed nut with a washer? Anyway, worth exploring all the options before starting drilling, a more scientific approach would surely be in order :)
I think @mdcc_tester will have all the answers!
If countersinking obviously you do it on the steel droput, I think something like this will do the job