Wow he's a great climber! I think he can see out of his enclosure and wants out! Lol. Don't you worry about him falling and landing on his back? It would scare me :S
You should add some dirt or something to the bottom, maybe he would be more inclined to dig rather than climb, However it is a russian so he may keep climbing instead haha.
I don't worry about him falling cause hes done it a few times and in a couple seconds he gets him self flipped back over. In his indoor enclosure he does both sometimes he climbs on his log hide to look at me to see if i am going to take him for the day.
The enclosure i use was something i put together in about 15 minutes and is easy enough to move and take down cause here in north Dakota our weather is a little unpredictable i am in the design process for his indoor enclosure that i am going to build just don't seem to have a lot of time to get everything down that i want to.