I'll look into this.
My HD Driver is ICD-PRO, because that's what came already installed on the SD card. Not sure how much RAM that is currently taking up. It's a pity there isn't a way to force the ICD HDD driver to load high, well out of the way of any area that Starquake is likely to want to live in.
In the meantine I managed to find Starquake as an .ST floppy image (not on its own, but on a compilation 'double' disc which also included a non-working 'Xenon'). Fortunately the disc is working well on the Starquake side.
If I copy the Starquake files from the floppy into a folder on the HDD and run it from there, it gets a little bit further but then predictably tries to load something from A: even though it has been run from HDD: If I insert the disc it loads what it wants to from there and then carries on without any further disc access after that, as far as I can tell.
If I can spare the time I'll look through that version to see if I can just patch the disk calls from 'use A' to 'use current drive' instead.
Starquake doesn't seem to do saved-games (which could be awkward and difficult to convert from FDD to HDD), instead it just uses location short-cut codes which you earn as you work your way through the game. So it's a good candidate for HDD conversion.