Panther uses a centralized
diskimages-helper tool for all disk image mounting, but unlike on Jaguar, there is no GUI acessible preference to enable skipping of the checksum verification to speed up mounting. So use the following instead (in Terminal):
% defaults write com.apple.frameworks.diskimages skip-verify true
This will turn off disk image verification system-wide, regardless of what client has requested the mount (e.g. Finder or Safari or Disk Utility). There are many other interesting preference keys as well as their defaults in
/System -> Library -> PrivateFrameworks -> DiskImages.framework -> Resources -> defaults.plist and client specifc defaults in
/System -> Library -> PrivateFrameworks -> DiskImages.framework -> Resources -> agent-defaults -> *.plist.