OK, I've been pretty busy and not spent much time on here, but I have a few thoughts.
I'm not saying the Campbell shingles/shakes look all that great.
BUT, going back to Matt's orignal comments, NO they would not be thinker.
#1 Perfection Blue Label western red cedar shingles are only .45" thick, at the butt edge, and the taper to near zero.
.45" divided by 87 = .005"
The AVERAGE piece of paper is .004" thick.
In my humble opinion, there are far too many people willing to accept over sized details, on structures or rolling stock, just so they can see them from too far away.
The texture of a roof, even a cedar, slate, or tile roof, is pretty subtle at our viewing distances in HO scale.
It's just like wood grain showing on the siding of a building. Unless a building is a neglected wreck, there is no wood grain you can see from 30' away, or the 260 scale feet that a 3' viewing distance represents.
And even when buildings had wood clapboard siding, you could not see woodgrain thru the paint at 6" away in real life, let alone 10', or 50', or 260'.
I HATE vinyl siding with molded in wood grain - so not what ANY old building EVER looked like when it was new.
Go out in the world, look at some buildings from 250' away. That might be a good standard for how your models might look more realistic.
Just my view, the view of the guy who builds models and restores old houses like these:
Even the slates on some of these roofs are less than 1/2" thick - remember .00574712" thick in HO scale.
Do you see any wood grain thru the paint on any of these houses? I hope not, my customers would fire me.
Sheldon