Hi John, I'll answer that with "Potentially".
Anything's possible. Keep in mind we are talking about press bent 2mm steel, so there would be some degree of work hardening in the mechanical bend to begin with. Could this propegate to a fatigue crack / failure long term? I can't say. If I were to guess, in 'extreme' situations (Think plowing thru dense fluids like water, snow, or digging the mudflap into deep sand), the bracket WILL bend- this is a given. To a greater degree, the nutserts would pull out of the chassis crossmember, but I'm just spitballing.
If your actual question is 'Have I calculated the risk of fatigue failures of the bracket with the mudflap stiffening plate'? No.
'Have I the means to calculate this'? No.
I did some back of the cocktail napkin sums here (which are probably wrong), but give a very rough idea of the forces at play. I don't think normal on road driving will pose a significant risk to the design of the proposed fix, or the factory bracket. Biggest risks would be water, snow, sand or backing into a really high gutter.
I'm happy to have someone run some sums if they are in a position to do so, but I'm not looking to throw $10K in engineering consultancy fees to deconstruct and critically analyse life, the universe and everything else, for a part which is essentially just a small run.
What I'm aiming to do (and most business people will understand) is make use of the economies of scale to get a product to those who want it at the best possible rate. Materials wise, It's cheaper, per unit, for me- and everyone else for that matter- to make a batch of 15 from a whole sheet than it is to get my plans cut on a unit-by-unit basis.
There's more than one way to skin this cat:
1) Side exit exhaust- permanent, and against ADR's
2) Extended exhaust - permanent, still has the potential for contact of mud flap against hot metal pipe
3) Run no mudflaps - temporary, but illegal (against ADR's)
4) Run a bolt on bracket like I proposed above- temporary, but potential for damage offroad or long term. Damage can be mitigated by running as a 'quick release' setup
So it's all a game of chance, which way people decide to go is up to them, but the offer is here if anyone wants to jump aboard. I think there's enough transparency above to help people make a decision?
I welcome any further suggestions, ideas and feedback :)

