Modern large-bodied, thick airfoiled planes with a 4stroke motor have no problem slowing down on the downlines. On my Mantis with 140DZ I rarely use idle during looping maneuvers (double-I, cuban, avalanche, vertical 8,...). The downside of this being that it takes far more power to fly the upward segments of these loops and the uplines of tall maneuvers than a slippery plane would require. But, that's why we are seeing 160DZs in 10lb planes, right?