Total RSA in PGP

Is it possible to use RSA all the way through a PGP encrypted message (do not use IDEA)? If so, how? I know it would take a LONG time, but it would make for a nice option. If not, why? Although, it might take "forever", why not make it an option for those willing to wait? Am I mistaken in believing RSA is more secure than the present hybrid? Thanx, --demon