I think you're still dedicating too much space to water, and should think about your land area more like a planter box than a raft, if you know what I mean. the corner piece should work in terms of space, I've never used that type of wood before.
also, mistervalves won't work as your filter return. (just to be clear) misting and filtering should be seperate systems. you can do a drip return from the filter, but the misters can't be used that way.