Leroy17,
I have Kumho 285/40/17's on the rear and 255/50/17's on the front. On my Harrison they fill the guard nicely with a similar gap from the lip of the guard to the top of the front and back tyre.
If you live around Brisbane try this company. They can usally supply Kumho's slightly cheaper than the delivered price from the Tirerack.
http://www.option1garage.com.au/NewTyres.htm