Idle furniturational speculation

I've been thinking of sprucing up the utility of our game space lately.  I remember seeing 2-level game tables, where the upper level is just for miniatures, and you put all your papers, books etc, on the lower level.  We end up only using about a 3x3 space in the middle for miniatures, with the rest wasted.  It's not a problem for indoor stuff, but big outdoor fights always seem too cramped.

I think it would be pretty simple to add a second level to our current table.  I'd just need 2 sheets of plywood 5 feet x 2-1/2 feet.  Then I'd need a bunch of legs.  I'd attach the legs to the plywood and then set the two little tables on top of our current tables, and we're done.

There's one question, and one obstacle.   The question is just how big the space between the two levels should be.  Too high, and it's hard to see things from our seats, too low and it's too hard to use our papers.

The obstacle is my very erratic building skills.  Sometimes things miraculously come together.  Other times I'm Homer Simpson making a barbecue pit.