Techtool Deluxe 3.1.1 fails in firewire target disk mode??

I wanted to run the TTD 3.1.1 volume structure test on my 12"G4 powerbook (10.4.8, 1.25 Gb SDRAM, 80 GbHD), but noted the suggestion in both the Macfixit and micromat forums (from Micromat techs) that it is better to run the program from a harddisk which allows for virtual memory (rather than a CD from the downloadable disk image). Attempting to follow another suggestion from the MacFixit forums, I installed TTD on both the powerbook and G4 ibook (10.3.9), booted the ibook and linked the powerbook to it in firewire target disk mode.

I waited until audible drive activity on the target disk had stopped in case some time was required, then ran the 'rescan volumes' option on the TTD menu, and tried to scroll down. In both directions (10.4.8 to 10.3.9 and vice versa) the target drive appeared on the host computer desktop, and subdirectories and files were accessible to the finder, but the target drive was not listed as a volume on the TTD list, so repairs on the target disk were not possible. It was even possible to start TTD from the target disk, but it, too ,only listed the boot disk of the host computer as available for assessment.

I described this to a Micromat staffer moderating their forums and he explained that TTD is written by them, but supported by Appl,e so I should query Applecare as to why it didn't work.

Any suggestions welcome.