H longifillis, are not that hard to find, i had one about 15 years ago, cost me 3 pounds, come from holland. seen them at pier years ago too.
There is a huge H longifillis at Blue planet aquarium, easy 36", had my hand in its mouth at one point, but thats another story. Id go with ARTC for out and out wickedness, heard of a 18' one killing a 24" rtc.