I loaded up my SDHC card with OS X 10.5.8, the iDeneb version which is all set up to run on computers with BIOS instead of EFI. Wouldn't even boot up, much less install.
Now I am going to try iDeneb v1.3, which is widely noted to work on the HP Mini 110. I will then have OS X 10.5.5 (i.e. OLD) working. Then I can download the iDeneb Combo Updater, which will upgrade to 10.5.7. Then I can grub around with several fiddly patches to upgrade to 10.5.8.
This is the method I was hoping desperately to avoid.