I've had 245/40 and 245/45 on my 17x9 wheels and were stretched. 265/35 on my 18x10 are stretched, but my definition of stretch would be different to say, yours, I'm guessing. I didn't say anything about 235/40 . The person asking didn't say anything about prices, plus 245/40/17 aren't as expensive these days. Yes 235/45/17 is cheaper as it's way more popular. That being said, would you want to run wider tyres that fit into the guards? I'm going to run 255/40/17 on the back of my R31 (17x9 wheels).
Picture was relevant to my "stretch" point (sidewall angle). 245 is slight stretch, 235 would be even more (that was my point).
Plus, 245/40 on a 17x9 +22 was made to fit on my mate's S14 with rolled guards, so that is a real world example (unless S14 guards have more clearance than R32).