R help - Mar 2006 - par(mfrow, fin) incompatibility?

Hello,

I want a 2x1 multi-figure, with each plot 5" square.
Test code:

x<-rnorm(10,0,1)
y<-rnorm(10,0,1)
par(pty="s", mfrow=c(2,1), fin=c(5,5))
plot(x,y)
plot(y,x)

but this does not work (overplots the two figures). Substituting pin for fin
works, but is not what I want. Are mfrow and fin incompatible?
I am basing my code on Fig. 4.6 in MASS4.
Running R 2.2.1 & WinXP.

Thanks
Dan Bebber

Department of Plant Sciences
University of Oxford