I think the Docs for Remus said ram-handler had to be run through a splitter program. Don't remember the exact details - I haven't investigated very thorougly.
At any rate, there's a patch on Aminet for the 3.9 ram-handler that tells you how much space is left in Ram Disk:. By default, it always says 100% full, xxxKB in use. With the update, it'll say 2% full, xxxKB in use. I'd recommend adding it to your image for a maximally updated 3.9 ROM :-)