Well from what I have done once it has Tiger it just won't go back. I suggest, before you go back, that you try this:http://www.sysresccd.org/Main_Page the PowerPC version.

If that doesn't work set that Clam into Target Disk, hold down the T at startup, and go on another Mac computer boot it from the OS9 disk and install it on the Clam that way.

Last if all else fails use SysRescue, to erase the whole thing and make 2 partitions. (It has to be MacOSExtended)

Install OS9 then Tiger.

Good luck!