The basic approach is just to see if GS/OS can understand the disk (i.e. if a VolumeGS call succeeds), and if not switch the order. We currently start with ProDOS order, then switch to DOS order if necessary. This is only currently done for 140k images.
Previously, we had actually been (erroneously) using the code for a generic hard drive, rather than a generic floppy as intended. The generic floppy code shows a 5.25" floppy icon, which seems less appropriate, so now we use the same code as 3.5" SuperDrives instead.
Stephen Heumann