Hi Kurama, I built mine about 20 years back and originally covered it in tissue, but it was far too fragile for slope flying. So what I did was to go along to our local full size glider field at Nympsfield in Gloucestershire and ask one of the repair guys if I could scrounge some of the lightweight heat shrink material they use. He gave me some big, for us, bits of the material and that is what is on it now. In the right conditions it flies really well, but make sure the C of G is correct or it is quite lively! Build the wings upside down as it says and be accurate.
The wing join is a bit strange in that it uses 4 split pins, 2 overlapping in each wing root, to give a hole to put a wooden peg down through the 4. The idea is that in a heavy landing it breaks the wooden pin and not the wing root. I used some 'lithio print' aluminum sheet for the cover for the centre section of the wings.
It probably won't let me post photos yet, but if it will here are a couple of photos of my Baby. It really is impressive in the air and as long as you are careful building it it will impress you too.