Good question Craig...one thought is the open top will increase the risk of the leg splitting, especially if the table was dragged across the floor. ...
Craig, I am not sure you can call 1/2 inch ample tenon length. With a seven foot table and 3 1/2 inch square legs you can get a lot more tenon length...
Well that solves the issue Warren. Almost all my mortises are only three sizes ( 1/4inch, 3/8inch and 1/2inch ) so I should have 3 gauges fine tuned...