Hello,
It sounds like your dimensions are okay. You definetely want the height for Taiwans. Given ample branching they are highly arboreal and with the proper temperatures and places to hang out they will often prefer to be up in the branches rather than on the ground. Now, that being said your male will probably start to outgrow that cage as he gets closer to achieving adult size. I have a male and female right now that are each housed in cages measuring 72" high x 29" deep x 29" wide.
My snakes are doing great in these cages now, however neither shows signs of slowing in growth, so I'm wondering how much larger I'll need to go should they begin topping out around 9 feet or so. Right now they're both about 6' or so. The only other thing I'd recommend is providing plenty of ventilation and lots of humidity. Not wet humidity but a constant level of around 70 percent or more.
I would also not worry too much about keeping your temps lower as many people seem to call for with Taiwans. Monitoring the weather conditions on Taiwan will show you it's hot and humid for much of the year. While there are cooler areas, it's uniformly humid and fairly warm. Keeping them in a fairly humid set up with good airflow, especially with a misting set up will help moderate your temperatures.
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Matt Campbell
Animal Keeper, Small Mammal/Reptile House
Lincoln Park Zoo Chicago, Illinois
Assistant Curator
Wildlife Discovery Center at Elawa Farm
Lake Forest, Illinois