4x2x15+
Oldest largest male colombian I have is 14yrs old, he's about 6' and most likely less than 15lbs, eats a jumbo about once a month. Oldest 'dwarf' is an 11 yr old hog isle, he's maybe, maybe... 5' and gets a med or small once a month, he is in a 3x2x2.
edit - add pics, these are the ones I am talking about to give you an idea:
bci (old photo)
hog: