I am also using supple nip. I don't know what size. But I wear them for about 45 min per day. It is slow and steady growth. I'm not aiming for huge, just a little bigger and more sensitive is the aim.
Been at mine 30+ years, incredibly slow growers, not even a full inch cold, yet... but only more seriously the past 5 or 6. I don't believe a normal guy could ever have nipples too large, and if into bodybuilding... well, let's put it this way: a guy with a very packed and large poser to go with all that muscle is more than desirable/admirable... as well as any man with huge areolae/nipples on a big muscular chest.
What I laugh at is these paragons of huge-muscled masculinity... and nothing at all of note in their posers, and pimples for nipples!! Looks ridiculous, to me. As far as tying off after, when hugely pumped, it helps a little and must be kept that way for hours. I do recommend getting the large silver sliders from nipplewrap.com. (Or make your own with some fair sized string, or fine shoestrings, with a slipknot. And never let them get dark purple or white, keep them a nice flushed pink.)
But too big for display? (Few would qualify, except maybe those on estrogen trying to transition.) But there is one black guy on nippleplay.com, biggest I've ever seen, pumps to 3.5 inches long, can kiss across the center of his chest. But they aren't attractive. very dark and heavily corrugated. Though to be able to suck/chew on them both at the same time, that's entering the realm of heaven. Whether it's you yourself able to be doing it, or a partner.... (And would be wondrously more so, if they'd lactate a rich nectar like pre-cum, or even actual milk. Like my boy Superman does/can in my stories on Telemachus: major source of his great strength besides his own seed, and the sun. Or the men in my novel, Chronicles of the Mighty and the Fallen. Hot, with a GOT ambiance.)