hi Paul, doesn't this question depend a lot on which wheels (and rules) you are running? the jaco/xceed wheels have less offset than the bsr/crc wheels, too bad the jaco availability is an issue lately. But more confusing is the rules.
the rules that i beleived to apply were the worldgt forumula at:
http://www.worldgtrc.com/ which has a 200mm chassis width and a 205mm width body limit, but the ROAR rules only state a 205mm width. all things considered, the IRS diff has a 1mm shorter right hub compared to the serpent part. wouldn't this accomodate the change in offset from the onpoint lower pod plate?
what would be more interesting is a wider rear brace to place the body posts further out. Also, when will we see some inline capable 1/12 items?
You might be ok with Jaco wheels but with the BSR You wont be able to get the track width centered, you can get it close but not perfect.