This is a mini version of my T4 Quadcopter design. It uses the same concepts but is completely redesigned to fit into the "250" class of mini quadcopters. This design is suitable for 5" props. If you are after something a little bigger there is now also the T4 Quadcopter Mini 315 that supports up to 8" props and a 2200mah battery - or just use the longer arms on this model if you don't need the battery space. Check out the whole "T" copter family: 2 September 2014 Legs for your T4 Mini are now available. 12 August 2014 Version 1.4 New vibration isolating top plate option. This option is compatible with previous body and all other components. It replaces the top plate with one that has mounting points for 65 gram vibration damping balls that then connect to a new floating plate to hold your flight controller and camera. New files: I printed all parts in PLA, 0.25mm layers with 40% infill, 2 shells and 3 top/bottom layers. Feel free to experiment. I didn't play around too much with the settings as these gave me a good strong result. Fitting the top plate and bottom tray Both the top plate and bottom tray are designed to slide from front to back (at 45 degrees) as they are being fitted into the body. In particular the top plate needs to be pressed firmly down onto the 8 angled guides as you slide it back. Once in place the top plate will clip onto the smaller bumps near the rear cable tie mount (just above the rear arms). Look closely at the parts and it will all become clear. Calibration test T4MiniTestSocket.stl contains a cut-down socket you can use for testing the fit of your arms before committing to the full Body print. A quick word about scaling According to Wikipedia apparently "there is no scale information [in STL files], and the units are arbitrary". There is often confusion with STL files and metric versus imperial (inches) units. I designed these parts in Sketchup using metric units and they import correctly into my slicer (which is also set to metric). If you have issues, check your application to see if has a way to select metric or alternatively scale down by a factor of 25.4. Also, the Sketchup file contents are scaled up by 1000 (attempt to solve some Sketchup quirks). I scale each component down by 0.001 before exporting the STL so they are in real millimetre sizes. If your new to RC copters then the ArduCopter wiki is a great place to find out everything you need know.