Doing the calculations on that page, (50-34)+(28-11)=33 max capacity required, while the max capacity listed for the short-cage is 29. The numbers can probably be stretched slightly (considering the page also says the short-cage RD can handle a maximum of 27 teeth on the largest cog), but someone else may know about whether a 4-tooth difference is too much. A standard 39/53 chainset would reduce that to 2 over the max recommended capacity, which may be more reasonable.