With the lack of responses, it would seem that their may not be many relic hunters in Northern Alabama. That could be good news for you. More relics for you to find!
I'm not in Alabama, but it seems to me that you might benefit from a detector with an adjustable ground balance and maybe even ground tracking.
I have a Minelab X-terra 70 and am very satisfied at the depth I get in my clay-based ground. For example, I have a Lesche hand digger which I can dig down to a depth of 9 1/2" maximum. I recently had to order a Predator Model 80D-Relic Pro spade because I often cannot recover targets detected by the X-terra 70. The Lesche hand digger can't get down that deep. These would be the larger size relics.
The X-terra 70 has adjustable ground balance, automatic ground balance (which I don't use) and ground tracking (which I don't use either). The X-terra 50 has adjustable ground balance also but not automatic ground balance or ground tracking. The X-terra 30 has a factory preset ground balance, like your Cibola, which may or may not be functional on your soil. I haven't used an X-terra 50, but I'm sure it would do great for relics with its adjustable ground balance. It apparently has the same depth as the X-terra 70, so they say. I like the 70 because I can use the two tone option, which I think is best for relics. It also has an interesting prospecting mode.