I' am using circos plots from OmicCircos to make some simple visualization of gene fusions. I want to make the font size of the gene names larger, but when I do this the gene names overlap. Any solutions?

My code. I use the cex parameter to control label size in the third function call of circos.

pdf("test.circos.pdf")
par(mar=c(2,2,2,2))
plot(c(1,1000),c(1,1000),type="n",axes=F,xlab="",ylab="",main="")
circos(R=400,xc=500,yc=500,type="chr",cir="mm10",print.chr.lab=T,W=15,scale=F,cex=15)
circos(R=350,xc=500,yc=500,cir="mm10",W=240,mapping=fusions.formated,type="link",lwd=2)
circos(R=445,xc=500,yc=500,cir="mm10",W=20,mapping=labels,type="label",side="out",cex=2)
dev.off()