I did the following on my P2: 1. Used a 3D printing 'pen" with ABS plastic to fill in the areas around the screw bosses under the motor and up to the speed controller, then filled in the "ring" around the motor, ( I used a "3Doodler", but any other 3D pen should work as well ) 2. Anyone who knows about 3Dprinting with or without a pen knows that adhesion is difficult unless both plastics are HOT. But I didn't care, because... 3. I used THIN CA to bond the ABS mount stiffeners to the phantom's shell. WHOA! did that make a shocking difference. I can pick up the whole phantom one motor shaft an it doesn't budge. When I have the time, I'll try so post a STL file that is the same shape, so that others can just drop them in, and glue them in. (maybe I should sell them... The arms still had a some torsional flex, so I did this: I applied THIN CA around the lenses for the LED's. I made sure that the CA was applied all the way around. That made the torsional strength skyrocket. I do know that doing this is a PERMANENT mod, but there is not really a good reason to remove those lenses, ever. I was able to raise the gains without issue, and greatly improved the stability - especially in high wind conditions. (it also makes better video when its flying at high speeds) Does the P4 have stiffer arms than a P2/P3? DJI did mention that the P4 has sport mode, and perhaps they stiffened the arms so that they could include the sport mode, and allow the P4 to fly faster.