I've been reading a bit of Dudley/Piers before, and this is one of the best, if not the best fic I've read with the pairing. Lovely, sweet (yes!) scene, quite precisely picturing the two as I imagine they'd behave in, well, a scene like this.
Very well written, and I particularly adored that you let Dudley stay the way he is - not prettifying or slimming him for some reason. Made the whole thing even better - and also hot. Especially these lines describe why Dudley should not be other than he is: The soreness was satisfying, perfect. The best part for Piers was the way he was so thoroughly pinned down, the way he could barely breathe. They rocked together beneath the sinking sun until everything narrowed to the urgent roll of motion, the simple imprint of skin. - lovely.