I've only cooked on my g2 chubby twice now and just got my party today and will season it up tonight, but here is a post I did on my first g2 chubby cook.
The g2 is deeper, but close in size. I use 2 cubes in the back like you did and I really like how that works. Once it was at 250 it held really well the whole cook and smoked for a long time. 12hrs until I went to bed and it was still going. Obviously the charcoal tray is deeper in mine, but the method of just adding unlit like you did works well and is how I know a lot of people do it.
I don't have much more experience, but will over the next few weeks. Doing a big cook Friday.