On the other hand, a smaller contact patch covers less ground, and the smaller radius tends to spit stuff out the side a bit...

Rim damage is more likely with a smaller tyre, but whether punctures are depends on a few factors.

Since 60% of your weight is on the rear, that wheel is weaker thanks to dish, and it tends to cop more bangs, it makes sense to run the next largest size tyre and even a heavier rim on the back, IMO...

An 80kg bloke could prolly get away with a 425g AeroHead if it's 36h, on the front...