I have 21 instances of Cache running on a single server.
There are a lot of pluses: simpler cpf, database snapshots, easier downtime negotiations
I would manually specify memory since you likely have very few simultaneous users.
Here is a link Sizing System Memory for Caché
If your session is text you might make a look at a tool like screen that is available for Unix based systems.
Death to extents :)
I work in Unix where LVM and mount points would make this easy but it looks like Windows has mount points.
You can compact and truncate the database while IRIS is up.
Truncating is the next section