Each to his own I guess?
But having driven on Australian roads for over 40 years and traveled over 3000000km in that time, in all sorts of vehicles, I know exactly why they make road tyres and track tyres and why profiles are so important.
With your 35/40 profiles on your 18 inch rims, I would recommend you buy a kidney belt and wear it everytime you drive. Your tyres are going to be so hard, your ride quality will be almost nil, you will be able to roll over a 5c piece and know if it's heads or tales, when driving on cement/concrete roads your going to be tracking the joins/expansion joints like nobodies business, miss cue just a little and clip the high side of a driveway kerb, or hit a pot hole and you're most certainly going to be buying another tyre and possibly another wheel rim as well.
As for semi slick tyres on the road, yes they are street legal, but only because they have grooves in them. The side walls are not designed to take ANY abuse, scraping/rubbing a gutter, or bumping a kerb and your likely to be looking for replacements. They do not like the heat cycling that occurs in road driving conditions, because once they reach operating temperature, they like to stay there, not get hot & cold like a road tyre. They are also going to have a 270kph speed rating when in Victoria, with more speed cameras than anyone would care to know about, get caught doing much more than 120 and your pride and joy will be parked for quite some time.
All seems a huge waste to me when other sizes are available and designed for the purpose at hand with costs significantly lower and therefore more economical.
I wonder if you or anyone consideres the insurance side of things??
Even Shannon's & Just Cars frown on anything more than a plus 1 concept. They will take your money and say nothing until it's time to pay out on a claim.
JMHO
D