It's repeated regularly that front opening Exo Terras aren't suitable for terrestrial Ts. However, the distance between top and front vents in a 12"/30cm cube Exo Terra is 8"/30cm. Why isn't that suitable for 6" spider (1.5x dls), or perhaps even 4" spiders (2x dls)? Not trying to be argumentative, I'm just wondering if there's something I'm not taking into account here?