First, with your current benchwork design, you have no chance of running O72 curves, even through an oval on the main portion of your plan. Your maximum width is 6' (72"), but to run O72 with clearance for engine or passenger car overhang, you would need at least 7' (84"). Second, given the width of your middle finger (of the 3 fingers), you can't even run O54 curves consistently through this layout unless you just run some stub-end tracks down that middle finger. Finally, I agree with Rusty; at 15" aisle width, you and anyone else walking down that aisle (you won't be passing anybody, though) will have to penguin walk sideways to move. And attempting repairs or working in such tight quarters will be just miserable.
I may regret saying this, but this is a classic example of putting the cart before the horse. Construct a layout plan to fit your space first, then build benchwork to suit. Squeezing a plan on to benchwork you've already built will be a very daunting task.
Chuck
