Ya, I think the 1mm rumor is something that has spread and was morphed from the original .100 inch (2.54mm) rumor, which is more likely, but still pretty small.
I just took my OEM battery out to measure it.
Thickness is about 0.175 inch (varies due to paper)
Length: 2.57 inch
Width: 1.725
Volume: 0.776 in^3
Ampere-hours: 1300 mAh
or A-h/Vol. = 1675 mAh/in^3
If we assume the same energy density of the extended battery, with the same length and width,
(2150 mAh / ( (1675 mAh/in^3)*1.725in*2.57in) ) = Thickness = 0.290 inch
So the extended battery will be about 0.290 inches thick, for a difference of 0.115 inches (2.9mm) over the stock battery
Add in the current thickness of the Incredible, 0.48 inch (12.2mm), the extended battery will increase the thickness by about 24%, for a 65% increase in battery power.
This is not fact, just an exercise in estimation based on our current knowledge.
-dibs
Ur not considering the fact that there are 1750 mah batteries the same size as the 1300 and 1500