"does it require an exagerated twist and lean to take full advantage of the blade length?"

No. No extraordinary body movements are necessary. Arms are kept bent a bit more and elbows are lower than the stroke with a fat blade paddle. Body rotation is used as "arm paddling" with any type of paddle will not get you far. The whole paddle/stroke combo is what I like to call a low energy system. An Inuit hunter needed to expend as little energy as possible getting to the place he wanted to hunt seals. After catching his prey he needed to expend as little energy as possible towing his catch home. It will be more evident when you get hold of a GP and try it on the water. The interesting thing about a GP is that it responds well to modern stroke technique as well as a wing paddle stroke. Very vesatile.