Oh, well then! You must know what you're talking about! Just because its all braced in motorsport application doesn't mean it's necessary for road use. It's obviously gonna be under much higher stresses in motorsport. Have you ever felt a 10mm thick plate? There is NO way that it will bend lol.
Of course there are higher stresses in motorsport...but fast road use isn't exactly stress free. Sure, if the car is a static show queen, it's unlikely to be a problem.
You could technically drive your car with only 2 wheel bolts holding the wheel on, as there aren't many stresses there when mooching off to the local Tescos...but would you?
10mm plate flexes...it doesn't have to flex much to throw the rear wheel alignment out, or to over stress the tightening torque on the bolts holding the drop plate to the rear beam leading to bolt failure.
As for the bolts, how do you think stub axles are held on in the first place? It's no different! As long as they're the right tensile there's no reason it would be unsafe.
The bolts are not the issue...it's the leverage on the bolts afforded by the 10mm plate.
Standard stub axles are bolted on with no leverage onto a fully braced section on the rear beam.
Besides, the plates that James has on his mk3 are a tried and tested product from a reputable company in the US.
Just because they are made by a US company, doesn't make them ideal.
There isn't a better way of keeping lots of suspension travel and being low, unless you get hold of some custom length strut bodies. Damping adjustable coilovers don't make a blind bit of difference when you're sat on the bumpstops, don't you thick race teams would have thought of that if it was the case?
I'm quite sure race team don't use standard dampers, or standard length coilovers...
In principle, the idea of re-locating the stub axle locating points is sound...however, it;s the method of simply bolting on a drop plate that is not so sound.
The pictures posted in the ClubGTI thread give examples of doing it properly, boxed and gussetted for strength...not just a 10mm plate bolted on.