I'm not a boa guy.
With arboreal colubrids, they are kept in large arboreal cages. Thrasops and rhamnophis in 4x4x2 cages with overhead RHPs, a ton of branches and several hanging birds nests at various levels. I have my pair of p. poecilonotus in a a 6'x4'2' cage and my spilotes pair in a cage of the same size.
P. Olfersii are kept in a 4'x3'x2' cage - same with p. viridissimus.
For comparision, single adult olfersii are housed in 30"x20"x20" arboreal cages.