somebeaches are hard enough to get growing good as it is...
biggest ones I ever saw were at Maple Hall outside Lexington VA about 8 years ago
I hear they trimmed them back about 50 percent
they were almost to the 3rd floor of the old home and were said to date back a very long time
In fact I buy down there, as they are less money, larger from a longer growing season and still fare well further north in a lower zone. They also keep their shapes pretty much are so thick and stay green, just have a row around a center section in a more protected courtyard; which I wish I could trim more precisely. Forget ever doing some topiary type animal!!
Home Depot early on in the season has some nice big healthy ones.
The illegals stand on the corners or at the food marts in the Hamptons, in groups and get picked up for massive ground care work. They are good at shearing/shaping.