countour blade for HD77 worm saw

Hi there,
What would be the right countour blade to use with a HD77 worm saw? Can I use the 5" Alpha with it? I need to cut an oval sink hole on 3/4" Granite (http://tanbrown.org) . The sink will be a top mount one, no need for polishing.

I used to cut square sink hole but not an oval one.

Please advise.
Trihai