tyre/rim size compatibility

Hi all,
I'm in the market for some new rubber and was checking out the BFG website which has a tyre size guide. For the AT's it states that 235/70/16's should run on a minimum rim width of 6", optimum of 7", and maximum of 8". For 235/85/16's it is 6, 6.5 and 7 which is also what they recommend for the 235/75/15's. I do not understand why there is an inch difference in the recommended maximum rim width between the 70's and the 85's which are the same width just different profiles.
Now I'm worried because I'm currently running the 85's on 8" Sunraysias. Is this dangerous?
Also if this is the case, it seems I'll need wider tyres than I have but they already stick out from the vehicle about 10-15mm and I really don't want to put flares on my standard 80 series and change it's looks (I know, beauty is in the eye of the beholder) which means I'll need to change the wheels as well.