If you are happy that you know more about the structural design of the tyre than the manufacturers and are happy to ignore their recommendations, then fine, but please take your chances well away from me when driving hard!
So do you never take more meds than the prescribed dose? completely different scenario yes, but same basis. Manufacturer recommendations are ALWAYS well below what could reasonably be described as safe. They allow a margin for user error, and then some. The ONLY reason a manufacturer gives recommendations in the first place is so they dont get sued should someone feck up royally! Its quite easy to quote studies and talk on a subject, but real world experience tells me that you can push tyres well past their recommended profile without issue.
As for stretching the tyre to avoid the arch (a common reason given), this says it all about the skill and knowledge of the modifyer. Very scary, they shouldn't be allowed anywhere near a tool set.
Now that i take offence to, actually making a car sit properly takes a lot more skill and knowledge than just slapping on a set of alloys and lowering springs. There is a massive difference between a lowered car, and a stanced car. Especially when using static suspension instead of airbags. A lowered car takes very little skill or knowledge to get right, a stanced car that is actually useable takes a hell of a lot more thinking!
Rim width, offset, spacer size etc all need to be taken into account so as to run the minimum tyre stretch possible whilst maintaining full suspension movement and steering capability.
Now dont get me wrong, there are MANY who run extreme stretch or/coupled with extreme camber just for the purpose of making the vehicle as low as humanly possible, this i am not in any way defending!
As with most things in life, moderation is key. But i maintain my standpoint, done correctly, I see ( and indeed have never experienced) any issues with tyre stretch whatsoever.
IMO