On how to convert the app to a self growing diskimage, I've found my way:
- launch the Disk Utility
- Click on "New Image"
- In the dialog window:
* Save as: type in the new diskimage filename, e.g. GuzziDiag-0.35
* Name: type in GuzziDiag
* Format : select Mac OS Extended (Case-sentive, journaled)
* Image format : select SparseBundle disk image
Click on Create
This will create a GuzziDiag-0.35.sparsebundle file and mount it automatically: you should now have a GuzziDiag disk image mounted.
Just copy there GuzziDiag-0.35.app from the zip file.
You now just have to run GuzziDiag-0.35 from the mounted disk image.
Unmount the disk image when you're done.
Just double click on GuzziDiag-0.35.sparsebundle to mount the image the next time you want to run GuzziDiag.