Just ran the Hyperion version under WinUAE and that was using about 50MB when I looked. I remember them saying how difficult it was to get Heretic 2 (ported before Quake 2) to work (mostly) in 64MB. Perhaps their Quake 2 source, posted on Aminet could be of use to you?
http://aminet.net/package/game/shoot/Q2Src