Very true. The problem is the spacers available. With a plain spacer you're normally limited to about 10mm (.4"). Then you can step up to the spacer/adapter type spacers that bolt to the existing studs and have their own studs, but they start at about 20mm thick and are more common in 1" thicknesses or greater. So, if you get into a situation where you need between a 1/2" and 3/4" spacer you've got problems. It's too thick to run a plain spacer, and too thin for a spacer with embedded studs.
I know the RMS is different and it depends a lot on your brake set up, but that 6.7" backspace could put you in a bad spot.