[R-sig-Debian] Now it comes downgrade or install two R versions under Linux

[Luis Ridao Cruz]

R-sig-Debian help,

Yesterday I sought help regarding R upgrading from R-2.8.1 to R-2.9.1.
I must thank specially Dirk for his helpful advice.

But now I am facing a dilemma. I want to install a package called FLR which
works under R-2.8.1. So my question is whether I can keep the latest release (R-2.9.1)
and also install R-2.8.1 (and if feasible how.)

Alternatively I could uninstall R-2.9.1 and just install R-2.8.1 but as the package installation is usually on-line
it might cause conflicts among packages and R releases?

Thanks in advance.