I agree, if you look further back in this post you will see Metzelers reply to my email asking the same thing and they recommended a 90/90 as they don't do the original size for the front, but they said to me on the phone that I will have no issues fitting a 90/90.
Other tyre fitting places I spoke to wouldn't fit anything other than the original size tyres to my rims. On the other hand there are hundreds of threads with people fitting 90/90 and 100/90's on the net and I haven't seen one about people having problems after doing so.
I was advised by many to stay clear of anything larger than above as it would cause steering issues, could make the bike lean over too far on the sidestand, as well as affecting the speedo etc.
each to your own I guess.