I like the folded dog bone design Kevin that you designed and Dave and Carl have refined, nice use of the space.
Is it your intention to have a 2' space around the back of the layout? I think that is a great idea for access for cars, switches, walk around space is often over looked so,I applaud you if this idea.
Around the wall layouts give you more running but you then need duck unders or lift out bridges etc. Your dog one is fine just tweak the grades to 6" max if possible.