Maltiness and body are two different things. I correlate body primarily with FG, but in addition to higher mash temp., that is a result of malts (e.g., crystal malts, unmalted barley) and yeast strain (attenuation). You could have a beer with an FG of 1.008 and plenty of maltiness and a beer with an FG of 1.020 with little maltiness. I think maltiness is more due to the types of malts used (e.g., pilsner, munich) and/or decoction mashing... and to a lesser extent, the yeast strain (cleaner yeasts may allow more maltiness to come through) and hop schedule. If you do a single infusion mash at 156-158, you'll definitely get more body than 150-152. But I don't see how those temperature differences alone have much of an effect on maltiness.
