We have a 100 year home. The vision is a tray ceiling in the dining room...with crown moulding on both levels, and a medallion in the center.

The room dimensions are 13'9" x 13'3" the ceiling height is 9'3".

The question is...we don't know the proper dimensions for the tray..we were thinking 6" down and about 18" across.

Is there any formula we should follow? My husband does drywall so we will be doing the labor ourselves...just don't know the proper dimensions.

Thank you