Corns are opportunistic feeders in the wild and are capable of eating until they throw up. Just because he can eat two pinkies at once, doesn't necessarily mean it's good for him. However feeding double pinks is a good way of preparing to move him up a food size. If two pinkies leave a lump in his belly for 24-48 hours after feeding and you feed no more than every five days, then that's he's fine as he is.
If the lump disappears within 24 hours of feeding then it's probably time to move up a food size. Remember that as food items get bigger, you should feed less often. This allows their digestion time to work properly and makes sure they don't get overweight. A fat Corn has the same risk of life-limiting health problems as any other fat animal.
As a general guide, the item you feed should be no more than 1.5 times the width of the Corn's body (not the head or neck). Whilst they can eat larger, this tends to carry a higher risk of regurging.