I actually used the thinner T1-11 in the half of the shop that sports it (because of attractive cost) and honestly, if I were doing it again, I would have gone with thicker material. Since it's a concrete block structure, I only have "half-stud" firing for walls behind it (insulated) and it's been a little "wavy" over time in some places because it's so flexible.
Tom, you're correct that it's called LP SmartSide. It's .31" thick, according to Home Depot's web site and sells for $32 a sheet. They have primed T1-11 in half-inch for $39.
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The most expensive tool is the one you buy "cheaply" and often...