Well, I am no expert on the accuracy of the MR lightsabers, both the more expensive line and the FX sabers, but you can always attempt to find someone who has one who is willing to take detailed measurements for you. I suspect they aren't perfect, but they could be close. Again, depends one what you are looking for. If it helps any, I own an FX Anakin ROTS.
There are members of the board who had contacts with MR's development team and might have more information about the actual props. SD Studios might be a good member to ask.