Instead of 1x stock for the supports,
which I didn't want to spend much money on, I bought a couple
of 8 ft 2x3 spruce studs (only about $1.50 each) and cut,
cured and shaped them to take any curl out. Another feature
which adds to the tremendous durability and economy of this
version are matching dados that straddle the T-tracks.
Well I hope you find this version useful. It probably takes
longer to make mine than Gary and Greg's, but mine is a lot
cheaper: I guess I only spent $55-$60 on hardware and a couple
of 2xs. All the other wood was leftovers.