Hello

I am making a few bookcases for the local school. They will be made out of
3/4 (18mm) birch ply with a 1/4" plywood back in a dado and 3/4 x 2" poplar
frame on the front. Two of them will be 2 feet wide by 5 feet high and the
third will be 32" wide by 6 feet high.

My question is should I make the middle shelf in each permantely attached,
dadoed to each side, so that the cases will not warp over time? If it
matters I will use shelf pins for the shelves.

Thanks

Larry C