Gross Weight

"once you go over the max weight,
you are essentially a test pilot".

That's putting it a bit strongly. As long as the CG issues are OK, the
effects of being reasonably over-weight are quite predictable in terms
of stall speed, take-off requirements etc. The structural issues won't
come into it as many aircraft have their max gross determined by other
things (eg. stall speed low enough for Part 23, or the need to
go-around at max gross with full flaps) and in any case, there's a
large safety margin in there. The fact is that assuming you're not on
the edge re DA or runway length, 5% overweight is going to be safe. It
isn't legal, but it will be safe. As to the arguement that breaking one
rule leads to breaking another, with respect, that is nonsense. That's
like saying speeding leads to murder...