Thanks for the replies guys.
I agree it needs more height. I'm not sure about putting that other piece of wood back in. It's massive, and I think it will dwarf the other piece of wood... But still I do need to add something.
I still have my micro swords - one of the them is in there, in the off-centre behind that rock. I can add more, definitely. Where do you think would be a good place?
And the substrate does have a slope - should I slope it even more?