Not sure I understand. Can you specify:
1) Listing of your drives, and remaining capacity
2) Are all your Aperture images managed, referenced, or a combination. On what drive does your Aperture library reside? On what drive do your referenced images reside (if applicable). Do this for each Aperture Library
3) Where do you want your Lightroom catalog? Where do you want the images in Lightroom to reside?
4) Do you plan on maintaining your Aperture Library (and duplicate images, if applicable)?
There are several options. The one that takes the least amount of space involves using all referenced images in Aperture and leaving them in place for Lightroom.
1. Macbook 500gb drive, 70gb remaining. 4tb drive 800 remaining. I have other drives but they aren't applicable
2. Managed, on the 4tb drive.
3. On the 4tb drive.
4. I do not.
I have the space, but the plugin doesn't change the available space statistic when the destination is change. So since the default destination on the plugin is on the macbook drive, the plugin always lists 70gb and does not let me proceed.
Very sorry about the late reply. Was having issues posting to the forum and forgot to come back.
What I'd do is relocate all your managed images to "referenced" on the same 4tb drive. In doing so, make sure you choose a folder/file convention that will match the physical structure you'd like to see in Lightroom. This choice is not mandatory, but is helpful. Note: If you convert managed images, they'd just wind up in one locatino.
I should have asked what size your Aperture library is. If you have space for all your images a second time over, then yes, you should not be seeing this error. But if you're using the plugin on a library with many managed images, the plug-in needs to copy those images, even if it's on the same drive, to a location outside your Aperture library. That's why it's helpful to relocate them as "referenced" images before the conversion.