I've run tires inflated to their sidewall-stamped maximum for wear, fuel economy, and handling purposes on various vehicles for probably 300,000 to 400,000 miles and they have been much more blowout resistant. Blowouts on modern automotive tubeless radials happen mainly for two reasons: Low pressure that causes high temperatures, or impact with a sharp edge that crushes the tire against the rim. Higher pressure protects against both of those blowout causes.
I've never experienced cupping. In fact, since I begin inflating to the tire's rated maximum, I've had perfectly even wear, which I never achieved before. Theoretically it can cause center wear but that consequence has not materialized for me.
At low RPM, a heavy foot is good, believe it or not. A light foot = a nearly closed throttle, which wastes a lot of energy as the engine sucks air through it. Low RPM + heavy foot really helps, so I wouldn't worry too much about the current tire size being too large as long as it's not tough on you or your clutch.
http://www.miata.net/garage/tirecalc.html is the standard tire size calculator. Check it out and be sure to calculate your speedometer/odometer error in to your fuel economy calculations, considering that your tires are not stock size. It says your speedometer (and therefore your odometer too) reads 8.6% too slow.
26psi is terrible for that. It's the minimum safe pressure to keep your tires from blowing out when they're brand new and not the defective Firestones that came on Ford Explorers. There's no way I'd ever run 26psi with any tires on that vehicle.
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