Please choose the program that is appropriate to your machine configuration. However, if you are having difficulty with the PowerPC native version, please try the 680x0 version.
OAT comes preset with a default application memory size of 1250Kb. The actual memory required does in fact vary, and often you can set this value lower (around 750Kb is the minimum). In order to do this, you should change the memory size in the Finder's Get Info window:
If you are intending to use OAT's Mail Compression features, you should leave the partition size at its default, since the compression routines use a fair amount of memory.