I am interested to find out what volumes of data each of these solutions, Cubes and Bubbles, have been tested against?

I work with enterprise tools to create ETL and OLAP solutions daily and really like what I see here but I am concerned with the performance since it is all done using Python and performance is not Python's strength.

Do you have any more information regarding this?

As an interested user of your project I would be more than happy to see a sign/text on the github project page that this project is temporarily on hold/abandoned, I'm a little annoyed every time I find an interesting project with no commits in the past year and other users asking the question if the project is dead in the "issues" section but still get no answer. I know it's open source and I know you do this in your free time, but still, just let me know.

And if your looking for a maintainer to take over then also state this on your page, unfortunately the outcome and success of a new project owner will not be in your hands. It's like your child growing up. :)