It's not just about your model fly. It's also about how you test it.
This report describes a quantitative larval crawling assay that reveals impaired crawling in disease models of Alzheimer's disease (AD) and Fragile X syndrome. They also note that their findings with shaggy mutant animals might be relevant to the use of GSK-3 inhibitors in treating AD.
Jakubowski B, Longoria R, Shubeita G. A high throughput and sensitive method correlates neuronal disorder genotypes to Drosophila larvae crawling phenotypes. Fly (Austin). 2012 Sep 19;6(4). PubMed PMID: 22992470.