I have my male BCI in 7,2 long x 2,60 deep x 4,60 high enclosure. So i guess i could give normandcass an advice out of my own experience. You can see that although i have a high enclosure, i have provided enough floor space. Your floor space is not sufficient i think for 7 and half foot boa. For such a boa you need 6 feet long or more enclosure. I have the humidity about 45% to 50%. Its hard to get it higher in such a big enclosure. This is an acceptable humidity level for boa constrictors when they are not in shedding. When my BCI is in shed, i raise it to 70%. This is a must. I achieve that through misting the cage several times a day and reducing the ventilation in the last 2 to three days of the shedding process. I have also real plants in the enclosure. Certainly you can provide as much height as you can afford for a boa as long as you you provide a sufficient floor space cause its more important.