As SH4 patched up doesn't require a registry entry, you may search in vain.
Many use multiple installations. Take a copy of SH4 install, rename folder and you're good to go = no entry for those "copies"...
And the same group most probably use MultiSH, so you can't even be sure what the save folder is named anymore!
At present I use 3 save folders: SH4, TMO and IXD...
The same group will probably also pester you for making your mod being able to keep track of/seperate their installs/data...