I know. There are many options. I just want to make sure you knew there could be an issue with getting a shelf and planning on a RHP. Half a shelf sounds like a good idea if they can do such a thing.
I had a King long ago and he climbed often. Im sure yours would mind some climbing stuff either. But you have to realize that being only 12 inches tall is going to really limit any real climbing. For $45 more you could get the T10 which is then the same size except 15 inches tall. I would have done that but Im putting two Bloods in mine so they don't need the headroom.
15 inches is still a good height to be able to use a RHP but much more than that they are no longer recommended unless it is for an arboreal snake.