From what I can read, Thomasville citrange is hardy down to 10*F. We do get those occasional winters when we have zero degree weather. The upper Gulf Coast satsuma business was wiped out in January 1982 ice storm and was hit hard again in March 13, 1993 snowstorm of the century. If you are south of Shades Mountain, you may be in a micro-climate zone 8 but Bham is actually Zone 7B. If you are north of Bham, Roebuck, Center Point, Gardendale, Pinson Valley, etc.; you will be in a very cold micro-climate fed by cold air from Sand Mountain. The Pinson Valley are is often 10* colder than the Weather Bureau at the Airport Protecting a tree may be a problem. Petals from the Past had a nice selection of citrus last year. You might also try http://www.justfruitsandexotics.com/Citrus.htm in Crawfordville (near Tallahassee), FL.

Very interesting. What types of citrus have people in this area had success with, if any?

Also, I don't have the book with me, but I want to say that I read that the Thomasville was hardy to 0 degrees in the Southern Living gardening encyclopedia, which is what got me interested in it in the first place. I didn't want a kumquat or mandarin orange tree that was only rated to 10 degrees and I'd really like something I could eventually eat off the tree. I saw a dealer in south carolina that said their Thomasville tree survives to 5 degrees once established (here, scroll down to Thomasville: http://mckenzie-farms.com/photo.htm). I like the fact that when not yet ripe the citrangequat can be used as a lime and when ripe it can be eaten as fruit.

I am south of shades mountain, so likely 8a. Am I crazy to want to try to grow one of these?

It's your dime, spend it like you want. I just wanted to state the facts so you won't be disappointed. McKenzie nursery says 5*, Just Fruits says 10*, Floridata say 0* for Thomasville citrange. 40 years ago the Univ of Florida ag school had citrus groves along I-75 a few miles nortu of Gainesville, They were trying to develop and marke a cold hardy citrus. Those groves of experimental trees were not commercially successful. A young man at Petal from the Past in Jemison was telling a man from Alabaster that a citrus tree he was looking at would survive winter in Shelby county. Go to Jemison and look at what they have, ask questions and ask if they will give you a one year guarantee like Lowe's does.

All the discussion seems to be about the absolute coldest temperatures reported by different sources.
The problem is, these are just "rules of thumb". If a tree is rated by someone as "hardy to 10F", that does not literally mean at 11F it will survive, and at 9F it will die.

A tree rated at 10F might die at 25F if it shocked by a sudden freeze. The same tree might survive 2F in another location if it is in a microclimate.

People pay way too much attention to the "rated temperatures", when what they should be doing is deciding how much work they are willing to put into it.

IF you are willing to put even in a little work providing protection in the winter (especially during the 1st 3 years of life of the tree) then they will be much more successful than someone that just chucks a tree in a hole and ignores it.

By the way, I have two Satsuma mandarin trees in my front yard in North Georgia. On average these are "rated" at 22F or so, but I've seen them rated at 15F in a few places.
Mine have lived through 2 winters so far with lowest temps at 10F, with NO damage. Of course, I built a cold frame over them the last two winters, with supplemental electric light heat in the coldest nights.
The result is I have had to build and actual greenhouse this year because they are getting to big for anything smaller.

What about trying a citrumelo?

Curious if you ever planted anything?