radial.plot shaded region

...
There may be a solution using the radial.pie function, and if I find it,
I'll post it.

Hi Steve,
Here it is. Just call radial.pie twice to get the annulus, then call 
radial.grid with the appropriate arguments, and then you can add 
whatever radial.plot you want, using the "add" argument.

radial.pie(3.5,sector.colors="lightblue")
radial.pie(3,sector.colors="white",add=TRUE)
radial.grid(radial.lim=c(0,3.5),grid.pos=seq(0,3.5,length.out=8))

Jim