Sorry, but isn't the disc spinning in this case? Also i guess, on most fat ps2s(all before V9), it will freeze on the playstation logo as the ps2 does a disc check at this place.I only know of this method:(only works on V9/10, maybe slims, don't know)1. Insert retail ps1 game2.
Go to the Browser, let the Browser identify the disc as ps1 game3. Start uLaunchELF4. Make uLaunchELF stop the drive(spinning of the disc)5. Swap for the backup6. Select, boot disc, or what's it called in uLaunchELF.