unfortunately i'm not working with a vxworks cam. i could...but i'd need to somehow bring the lessons learned back over to dryos.
Ok. The Lua free memory check command will actually work (partially) on dryos too, but it will use the crude brute force malloc test algorithm used in CHDK's misc menu memory info. It works (I've used it for checking things with sunsetF15) but should only be used for debugging things like this (i.e. not for logging between each timelapse shot for fun in a finished script release) because it fills up the largest available RAM block entirely before freeing it again, which could cause problems with other tasks Canon firmware may be running if I'm not mistaken.
Btw, do read that RAM page in wikia if you didn't already. To summarize what you might learn from there is that while testing this script you may want to always start it from a known steady state condition (and when using too if you indeed are short of RAM): you could start the camera to play mode, wait until camera is idle, switch to rec mode, wait until idle, shoot once, wait until idle and then start the script. Never start the script twice in a row, always power off and on in between. This all is to minimize RAM fragmentation. That one shot before starting the script is quite essential, half shoot is not enough.
Anyway, good luck...