T12-05 was preformed in the kit, I basically just smoothed and deburred it.
T12-06 and -09 are made from a 0.060" 6061-T6 Aluminum plate. The exact dimensioning and getting the angles correct was a little tedious, but not too difficult. -09 may end up being a little short before the bend, and I left both pieces a little long after the bends, to see how they mated up before cutting them down, so I'd have a little wiggle room if needed.
I marked both pieces as "long" with an arrow pointing to the long dimension, so I won't get confused later if they don't want to fit for any reason.