http://www.discounttire.com/dtcs/infoTireMath.dos
You did get me on the hundreths!
Those figures were rounded numbers but if you didnt see the full digits you would not know better, so I don't blame you. I thought you rounded yourself and wondered why since they are so close.
I would not go anywhere lower than 50 series or you are getting into rubberband thickness tire territory that does not look all that good on a VX.
I am pretty sure the offset and backspacing of these are the same as my ProComps. Nothing to be afraid of. I am glad someone is taking advantage of the link of tirerack's sales that I posted a month back. You can online check if they have a full set avail. It says it under the description.