Nuts,
The Magura, PT's, and Renthal Fat Bar are all made by the same supplier with different labels and finishes is my understanding, and none of these three are twin-wall construction.
Renthal does make a Twin wall, but this is a different bar and is laminated as you point out.
I also agree that flex is a part of every bar, however keep in mind the PT's are "engineered" to provide a certain amount of controlled flex with the cross-barless design, something that sets them apart from welded steel crossbar and bolt-on aluminum crossbar offroad handlebars. Taking an inch off the flexible part, the 14 inches outside of the bar clamp, is over a 7% decrease in the length of the lever. I can see where that may have an impact on the flex.
All that said, if you want to whack an inch off them and all the parts will still fit, then go for it. The flex is probably a bunch of marketing BS anyway :confused: .
As far as the tubing cutter goes, I find a hack saw with a fine tooth blade to be easier for this operation. I broke two tubingh cutters before figuring this out. Just dress it with a file when you are done. If you are a plumber or have access to the big iron then great, but your average copper tubing cutter does not work too well.