Take a look at the drawing by James E. Ivey. It shows a hypothetical altar screen over the main altar; similar arrangments of sacred art, like Holy figures painted on pine panels (retablos) and carved wooden statues (bultos), would have been over the side altars.
Did you know?
Archaeologists found pieces of a mineral called selenite on the floor of the nave. They believe they were used in the windows of the church, because it is translucent and would let light shine into the church.