Typically, RME will delete the old IOS in favor of the new code if the flash is not sufficiently large to hold both.
However, for these models, if you are using .tar images, RME runs the archive command with the /overwrite flag which will overwrite the previous image directory with the new one. RME will also manually remove files from flash based on a pre-configured ruleset.
What version of RME are you using? Have you actually tried deploying a SWIM job to one of these switches? What error did you see? What was on flash to begin with?