I think most people realize there's no such thing as a "true 35," or any other "true" size for that matter. Tire sizes are only a classification to allow comparison and check for fit, but they aren't an actual measurement. Even if they did all measure 35" diameter before being mounted, when you take into account different wheel widths for mounting them, tire pressure and the weight of the vehicle, the diameter would have changed too much to make that an accurate measurement anyway.
I agree that as long as the tire is only resting on the bumper it may actually help reduce vibrations, but if it causes too much pressure on the bumper it could actually be more of a problem than help (causing stresses to be transferred to the upper part of the tire carrier, problems closing the tailgate, etc). That's why I'd want to actually see pics or hear from someone who's done this.
:worthless: