@DrAzzy thanks for the response . . . I figured the hex with bootloader was pointless, but I didn't know it wouldn't work.
I do use your core. Thanks for all your work on it! I might have an old version of it . . . I'm not sure how to tell which version I have from looking at the readme.md file - it says it's for Arduino version 1.6.x, so a bit at least. Did you add the feature of deleting the non-usable hex later?