With a bit of work it could be possible to use the new u-boot loader to boot beta1 from SD:
gate the uncompressed vmlinux image fro the beta1 kernel and turn it into a ppcboot image (read u-boot README for this),
save the beta1 root home ... filesystems to mmcblk0p1 (formatted ext3)
etit the etc/fstab on the SD to patch the new root location (and any other filesystem you need),
install the new u-boot.bin image emerg system and kernel to internal flash,
reboot and hold down the "power on" button,
place the beta1 ppcboot kernel image where the beta4 kernel would be,
make sure the SD containing the beta1 fylesystem is inserted reboot and hold "1" button
I have not tested this but if someone gives me the uncompressed vmlinux image for beta1 (I do not wnat to recompile kernel just for this reasonyet) I can do some testing. Currently I'm booting my modified beta4 version from SD so chances are that with some limitations it could be possible to have beta1 booting from SD.
Regards
David