Just finished two of these heaters at an asphalt refinery down in Savannah, Ga. Total size of the lettering was 22' x 8'. All painted from a lift, no vinyl used. Used pounced patterns and latex paint.
Felt good to do this, very satisfying. Not counting the layout, actual painting time was about 5 hours per side.
Still have to do a water tank, it will be about the same size layout.