light Weight ceiling treatment

Looking for suggestions for a light weight ceiling material for a pole barn. It has a truss system on 8ft centers with nailers on 30" centers for the metal roof. I insulated with foam board and added additional 2x supports between the nailers so I have supports every 15". I want to do it as a cathedral ceiling and will only have an end wall truss a center truss and an interior wall built against the next truss. So the floor area is 16ft wide and 30ft long, the trusses span the 30ft length. I've considered a metal grid system with the lightweight flimsy tiles but looking for other ideas. I'm not against using those cheesy faux styrofoam beams to hide fasteners on a sheet type of ceiling, but not sure what to use because of the limited structural support.