Brian, That drawing is a little too notional and I probably shouldn't have thrown it up. The boss was calling me for dinner and it wasn't going to be pretty if I had trouble hearing her...
You guys had some good points and I need to look closer at all the changes but I think this is worth a good look.
FWIW, that leg is 4" x6" which I think is pretty massive. The tenon at the top of the leg could easily go 2" thick so there should be room to tailor down some dimensions without taking away too much strength.