This is a sleek handguard for G36 airsoft rifles. I have only tested it on a Umarex/Ares G36, so I can't guarantee fitment on other brands (TM/JG/SRC/etc).
It is based on pictures of the Spuhr R22 rail (which will hopefully make a bunch of Swedish SOG-airsofters happy) with modifications to cover the holes that airsoft G36es have unlike their RS counterpart.
It will fit a 3 piece nunchuck lipo (to my great surprise), but it is fairly tight.
For the optional rail pieces you need M4 counter sunken screws, or, well, glue if you are not planning on removing them...
Update: I tried it on a JG. Dimensions are a bit off, so I uploaded a new one named R22_JG.stl with dimension that should work better. You will however need to get rid of the flaps sticking out on each side of the gas block for it to fit. Otherwise it will stop as soon as it hits them. I perfomed the operation expertly with a pair of pliers on my SL-8 to make sure it fit :)