With the 285, or the the skinny Kumho 35x12.5, you could probably run stock backspacing with the CST, which is 5.5", about 25mm on an 8" rim. On a 9" width, for the same 5.5" backspacing, that would be +12mm offset.
Although there have been some that have fit 295's on stock rims, with the CST spindle, to allow for airing down, I would go with a 5" backspacing, (probably even with the skinny KL71's, in case I wanted something else latter. On a 9", a 5" backspacing is 0mm offset.
There are a few Procomp rims, (at least in the 17's), with 4.75" backspacing and 8.5" width, that would stick out 1/4" less than a 9 with 5" BS ... the more they stick out, the more likely it is that they will rub at the pinch weld. I run 8" width rims with 4.5" backspacing, so they stick out an inch more than the OEM 8" rims, and had 305's on them, but with just a leveling kit, had to do the pinch weld mod, see the link in my sig. Also, unlike the bracket lifts, the spindle lifts don't move your front wheels forward by an inch, so mudguard and pinch weld rubbing is more of a concern.