Only way to know is try it.
If you have frugal installs of each one as separate folders.
You could try using the save from Fossapup64 9.5 as the save for F96-CE_4.
See if it has any issues.
Just make a copy of the Fossapup64 save and place it in the frugal install of F96-CE.
Boot using the save.
To make sure F96-CE is setup to boot using a save.
Boot it fresh for the first time.
Do nothing but shutdown making a save.
Make sure to make same kind of save as Fossapup64 is using (save file or folder).
Boot Fossapup64 so it is running the computer.
Delete the save in the F96-CE frugal install folder.
Replace it with the Fossapup64 save copy.
Then boot F96-CE and it should now use the new save.
Seems to be using the same name for the save in each version.
So no name change is needed for the copied save to work.
Note:
Usually you can not use a save from one named Puppy in another named Puppy.
But F96-CE is an updated version of Fossapup64, so good chance they are compatible enough.