Feature requests

This is a really nice project, great work mate.

Would it possible in the future to add the following?

1. Add an option to cancel in progress generation.

2. Set the default image size to 256x256 if < 16GB system RAM?
This would be handy as 512x512 is basically unusable time wise on 8gb.

4. This is more of a question, but I know there are optimised low ram versions of SD, is possible to give the option of using an optimised version?