Gaunlets of Crushing add +4 to your THACO(in addition to fist bonus), but do not add +4 as far as what's needed to hit.
If you need +5 weapons in order to hit an opponent, and your monk's fist are +3 and he's wearing the GoC +4, then he can still only hit creature's who require +4 or less. In that respect it's not cumulative.
Again, this has rarely been a problem. Your monk gets to spend proficency points when leveling up like anyone else. You'll find a suitable weapon(s), and use it when needed, but your fists, by far, will be your favorite weapon.
You'll spend much more time scraping evil doers DNA from underneath your fingernails, than off a weapon. Trust Me
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An elevator smells different to a dwarf.
"The object of war is not to die for your country but to make the other bastard die for his."
-General George Patton (1885-1945)