I have yet to see a raised in captivity Suriname BCC exceed 10 feet. I've seen several wild caught exceed 10...
While it is impossible to file all Pokigron boas into a size window I can tell you about a pair I have. They are from different parents and were raised provided with long winters...I don't feed adults during winter here for several months when not breeding. The female is a 14yo and about 7 feet. The male is a 9yo, right at 6 feet and less than half the mass of the female. For only being a foot shorter he looks very small next to her while performing manly duties during his winter visitation.
Neither of these boas has defensively taken a shot at me but both will bite anything that moves when prey scent is in the air. One exception to that: the female is a complete monster when I take the babies out of the cage...seriously, I do not look forward to that interaction. Thankfully as soon as the babies are gone she is right back to her old self as if you flipped a switch. The male is a little shy and mostly low light or nocturnal mover. He will come to an open door to investigate movement but not with the same confidence as his fearless girlfriend.
These two and their young have never been ill, had a regurge or offered any trouble -and that seems the norm from all I've heard about Pokigron boas. They do require a little bump up in the humidity if they happen to shed in winter here (MN...very dry in winter). All Suriname/Guyana boas should be fed mice the first year and these are no exception.
Me personally, I would keep a male Pokigron in a 6x2 and raised properly I would fully expect him not to outgrow that size enclosure. The key is raised properly. Your comment of 'grown to breed' likely means something different to locality boa keepers... Rapidly grown boas (especially Suriname/Guyana boas) do not make good breeders. I don't care for the term 'slow grown' either. The best way to raise a boa is by observation, provide seasonality and alter the amount of daylight to coincide with those seasons. Feed more in summer and less in the winter and as they get older less and less feeding in winter.