How should I make this cross?

I am in independent study at my high school and I am doing it in woods. I am a huge metal fan (AC/DC my favorite, but Sabbath, Iron Maiden, the stuff my mom grew up with...). I am making a cross which will hold the letters spelling Black Sabbath. Black is going across and Sabbath going down (the A in black and the first A in Sabbath match up).If you dont know what i mean when i say the A's match up, look on images. I want to make the cross 18" wide and 24" tall. I am having trouble figuring out the dimensions because the letters have to be equally spaced and the same size. So basically i need help with the dimensions and the letters. If you could suggest some dimensions for the cross, the spacing of letters and the size of letters that would be great, If you could draw and dimension it that would be even better, if you do draw it email it to fishing140@yahoo.com. Thank you.