After cjc pointed out to ask the question at apple.stackexchange.com, I did. When asking the question I got to a related questing answered by someone saying to try Carbon Copy Cloner.
Carbon Copy Cloner cloned the files via FireWire to my SSDisk no questioned asked, and everything is how it should be..
Here's the question I'm referring to:
Restore system from DMG (original source disk bigger than destination)
For those of you interested in resizing a disk image:
Make your disk image read-write in Mac's Disk Utility:
Mount the disk, select it and click new disk image. Select read-write in the disk image structure drop down and click save. ( My OS is dutch, so these are my own translations ).
hdiutil to resize the disk image:
hdiutil resize -size 100G /location/of/disk.dmg. You can replace 100G by the size you want.
Optional (didn't work for me), you can try to compact it:
hdiutil convert /location/of/disk.dmg -format UDSP -o /location/of/NEW/disk.dmg.
This creates a sparse image.
hdiutil compact /location/of/SPARSE/disk.dmg.sparseimage
This will try to free up space on the disk image.. If it works I guess you may need to resize your DMG again to lower the capacity (I'm not sure)..