I haven't found a shop that would allow to test this... They appear to all be oh so busy.
However, it's only a half inch (0.6") difference with the 265 so it should be fine.
The one thing though, is that it seems a bunch of people are relocating their rear HVAC lines... Not looking to have to do this.
Dealing with those lines is not as difficult as it may seem at first glance. In fact, it is not so much the lines that pose the work but rather the body metal flange which stands out about 1". The lines tuck against this flange almost as if the flange is there to protect them but I doubt it.
I had this "bulge" flattened on both sides because it is a very tight fit when even the 265/65x18 is fully compressed into the fender liner. With the modification there is much more clearance gained.
I also had more clearance created at the front wheel area where the steel bulged out at the lower sill near rear of tire. This spot is tight when on full lock turns and rubbed when using the Goodyear Duratrac in 275/65x18. Now there would be almost an extra 2cm clearance.
My biggest annoyance now is with the new air suspension compressor depth resulting in my Rover Specialties sliders not fitting on the side with the compressor. I have not test/attempt fitting them but it is obvious the newest compressor physical size and/or bracket structure hangs lower than the factory 2007 unit (replaced last summer under extended warranty).
This issue with the sliders is particularly annoying in terms of timing on my end with compressor replacement and recent slider refurbishing. While it would be a simple enough modification to make the slider have an extended section where they already had a little drop plate, by cutting out some of the steel, adding more depth, welding, etc.
Mine were rusting so 2 years ago I had them fully blasted clean down to raw steel, then galvanized, cured for 9 months, then got around to powder coating. This was completed just before the compressor gave out. I do not want to alter the integrity of the galvanization but I would like to re-fit the sliders!