Rated 3 out of 5 stars
You definitely will have better luck asking in other places (mozillazine, by example) by a more generic solution instead of requesting here repeatedly by such exotic feature. I don't know much about RAM disks, but I guess that using symlinks for the Brief's files could help you.
Sad Rated 1 out of 5 stars
While this add-on has been between my favorites over the years, the sad thing isn't that currently the version 1.5.4 doesn't work anymore with Firefox, but the lack of a single word of the developer about its status.
Then? is possible to survive a while with the (still working) development version 1.6b1; check a independent development keeping the version 1.5 compatible
or to explore the alternatives hosted in this site: Bamboo, Sage, Feed Sidebar, among a few others (And I don't want to mention the as-web-services alternatives).