This is an area of specialty for me. I've never met an RD that couldn't do 14-30 on back, but there's a ton of factors that weigh in, of course: chain length, chainring size and difference between big/little chainrings, chain stay length, RD hanger/claw length.
That DA above looks like to could stretch out a LOT more than it is in the photo. Take out a link pair and jump up another two (or probably four) teeth on the big cog.
