good luck with the 5 zigens! i've always loved the hyper 5zr wheels
19x8.5 will be the perfect size all around as most members have said and tires will depend on the brand since some 235/35/19 tires are wider than others. i recall running 215/45/17 on my old civic before, yokohama advan sport, lined them up with a friend's dunlop with the same measurements and mine were wider by maybe half to a full inch.
to answer your question on stretched tires, people stretch tires to fit massive width wheels on their cars without rubbing. a lot of VIP guys, drift guys and vdubbers do this. on a ferrari or porsche, you would rarely see someone running a 12" wide wheel on the rear with no less than 315 or 325 for tire width. for VIP, on a 12"j wheel, they'd run maybe 275-285 because the stretch of the tire will allow them to be massively dumped.
here is an example:
check the rear tire and wheel. with the stretch, they can now go lower and wider than most cars can. extreme fitments. (minor fenders mods may be in order)
this is something very popular in japan. not many people understand the full concept of stretching besides looks wise though