Hmm... I've noticed quite a speedup if you take the time to set up an SFS file system (rather than FFS as suggested by Cloanto) - nifty!
BTW, Gryfon - here's how you do it:
1) Start with Cloanto's 'Amiga 4000 PPC' template.
2) Create an appropriate size external .hdf
3) Boot with the AOS4.1 .iso
4) Start the Media/Hard Disk Toolbox in 'Expert' mode.
5) Pick your .hdf and click 'Edit RDB/Reinstall'.
6) Select 'Install/read configuration' at the top.
7) Click on 'OK/Accept Changes' -
you don't need to change anything Go into 'Edit Partitions'
9) Click 'Add/edit filesystems' then 'Add new FS'
10) Select 'smartfilesystem' and change the 'DosType' to 53465300
11) Hit Ok then Ok again and create a partition if you need to (make sure it's bootable).
12) Click 'Select filesystem/edit details'
13) Chose 'SFS' and change the 'Blocksize' to 512
14) Hit OK then OK again then save your changes to disk.
15) You're done! You can get on to formatting/installing now