We have a design for a principal rafter-and purlin timber frame. We are thinking about using 1x6 T&G finish under a single or double chip panel roof, but are not sure what the structural implications would be, or if the 1x6's could be pre-applied to the sip. If we were to use a 1/2" drywall as our finish in other areas, could that be applied to the panels prior to installation? And if so, would we need spacers over the timbers? Lots of ?'s, I know!!! Any information would be greatly appreciated.