If you want to fire hot loads from a Vaquero, get an older model or have a custom model made. If you want to take chances with your new model pistol, PLEASE, don't shoot it around anyone else. Maybe you don't mind fragments of metal embedded in your face and hands but shooters next to you probably do. BE RESPONSIBLE!
Comparing cylinders from one gun to another is NOT a valid thing to do. Even if a cylinder looks thicker than another, that doesn't mean that the alloy or formulation of the metal is the same. There are some metals that are MUCH stronger than others and hence, may be built lighter looking than others. Just the same, a heavy looking cylinder may NOT handle what a stronger (thinner looking) cylinder can handle. Looks does not do it here so don't be fooled by it.
As for the Elmer Kieth question:
Here is the reason why Elmer Keith loaded as he did BEFORE there were heavy or stronger metals used in modern handguns. LIABILITY! It's as simple as that. Yes, you probably can load your Vaquero hot if you like but the manufacturers know the statistics of duration of it handling loads like that. Eventually (some day, some year, some time
) something is going to give. That doesn't necessarily mean it's gonna blow up but something will break and cause it to not function correctly or at all. And if it does blow up, then you or the guy next to you is going to file suit against the manufacturer, all because the user didn't follow directions. Guess what happens after that? MORE RESTRICTIONS ON GUNS.
Give us all a break and follow directions and shoot safe and smart.
Thanks!