Hey.. quite embarrassed to ask this actually - I should be able to find this on Google, but because of all the new WP functionality as well as the older methods of doing this in older versions are riddled all over Google Results that I have resorted to leverage the knowledge of a good samaritan out there somewhere.
I already know how to set up custom thumbnail sizes (I'm developing a Magazine style theme), and at the moment I'm working on getting my gallery working. When I choose to "insert to post" an image, it gives me 4 options - small, medium and large thumbnails plus the original size.
I need to know, for embedding purposes (not the featured post thumbnails), how to set the default sizes of these thumbnails so that they appear in the Media section of the Post editing screen.
Any ideas?
I answered my own question folks, and I feel quite dumb.. haha.
It was in the Admin screen. Left bar.. Settings -> Media, and there they are. Thumbnail, medium, and large sizes. No file hacks, no custom size settings in the functions.php file necessary.
Oops!