I really like top cropping. I have found half a cup of good healthy top cropped yeast in standard gravity beers is plenty when pitched within a day. So healthy and active, and then they throw off more healthy yeast. Win win!!
I just top cropped some Burton ale yeast ( wlp 023 ). I cropped about a cup? of thick creamy foam, kegged my mild, dumped the yeast cake, then dumped my top cropped stuff back in, and whacked a porter on top. 3 hours later there is a nice pavlova on top of it. I also grabbed another smaller sample for using later in other beers. Too easy.