Bob
First, I would strongly suggest you not go anywhere near 4 feet tall. The 8x4 floorspace will be more than significant. I would not go higher than 2', and with all that floorspace, you could even go 18" with no problems. The extra height will only create heating and humidity problems, and she will only seldom, if ever, use it.
For My big females, I keep them in 8x 2.25 x 1.5 tall. My biggest female is currently at 13ft and about 60lbs.
For her max size, I dont know exactly. As far as albinos stayin smaller, I heard a rumor of a guy with a 19-20 ft female albino, so i dont know that this is true. There arent as many albinos out there, so the likelyhood of a larger animal is smaller than with a normal. But I think around 14-16ft is average for a female. Depending on feeding and other things.
Dustin
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1.0 Albino Green Burm
0.2 Normal Burm
1.1 Java Retic