As usual, dakski Dave gave great advice and insight. He's a fantastic resource. Thanks Dave!
...and to answer your question, Bredli females can get up to 8'+. But fed a more conservative diet Fernie will probably top out closer to 7'. They are typically a bit more stocky than carpets though, especially the females.
To follow up on a point dakski made, the 2 feet of depth allowing for a second perch allows you to have the perches at different heights and distances from the heat sources too. So not only will they have a gradient on the enclosure floor, but also plenty of options to thermoregulate when perched.