OP wrote:
what is known about the moments of this ratio?
I have not seen the paper ... but one does not even need to derive the distribution of the ratio in order to derive the moments of the ratio. In particular:
If X ~ $Beta(a,b)$ and Y ~ $Beta(c,d)$ are independent, then the joint pdf of $(X,Y)$ is, say, $f(x,y)$:
http://www.tri.org.au/se/Betajointpdf.pngThen, the kth raw moment of the ratio $\frac{X}{Y}$ can be derived immediately as:
http://www.tri.org.au/se/kthmomentofratioofBeta.pngwhere I am using the Expect
function from the mathStatica
add-on to Mathematica to automate the nitty-gritties for me (I am one of the developers of the former).