1/2.35 = x/720. Cross multiply and get x = 306. Subtract that from 360 height for 16:9 dvd video source and you get 54. Divide by 2 and you get 27.
Why is the template 720x486 and not 720x480?
I think 27 each is right, but I don't know why--you said making them 60 pixels each wasn't big enough. Maybe putting together your template with a height of 360 instead makes my equation work. I'm sorry I didn't come in with stock knowledge and instead calculated it myself (and might've calculated it wrong. But that's what I would do.