For those who don't know, I am building a full size R2-D2! I am using a Raspberry Pi for the brain with multiple Arduino Mega 2560s to control actuators and the like. It's been a lot of fun figuring everything out and I still have a long way to go.
The frame is aluminum. I got an older design years ago. I saw in your video that you have one of the newer ones.
Mine is setup to have the center leg able to retract/extend, and the side legs to adjust between 2 leg and 3 leg mode.
I have the same dome as you do, and several of the other outer shell parts are the same or similar.
Sadly, I have not done anything on it in a long time, been sidetracked with other things. I need to get back to it.