I think any enclosure or free range that is big enough and arranged in a way to not make Trioceros oweni as skittish as they can be would help. I would not use a standard 2x2x4 chameleon enclosure.
The problem everyone had with Trioceros oweni with this species being reclusive and temperamental was major problems acclimating to captivity. The two breeders that I know that received specimens did not breed because their Trioceros oweni never acclimated to captivity and died. Susan James (I have not seen her pictures of CB Trioceros oweni in a long time and I never talked with her before about her Trioceros oweni) is one of the few if only exceptions. Even though it would be great to watch more people follow in her footsteps.