I managed to install 10.5.7 on my Acer A150. I installed MainStage by editing the LogicStudio.dist in the install package.
MainStage 2 starts up, gives an audio driver error, but I can click continue. Then I get into the template chooser. When I select one and press continue, MainStage "unexpectedly quits".
UPDATE: Mainstage is working!!! When MainStage started up it gave me a "Selected Driver not found" error. So I looked into the MainStage preference file (with PlistEditPro) and compared it to the one on my iMac. On my iMac it has an entry:
OutputAudioDriveName <string> FireOne (0007)
So I changed the plist on my Acer One to have that entry as well, as it was not there. On the Acer I have a Numark, so I put the name of the device in there (Numark USB Audio Device). And voila! It is working now, woohoo!!!