While I, Nightwing was out in Poland Phobos showed him how he counter sunk his bolts into his frame by drilling out the plastic a little bit. Before, I used to mount my motors the normal way with the metal screws then use my soldering iron to heat up the screw until it would melt the plastic then carefully tighten the screw until it would melt into the plastic. This would fail if I wasn't super careful while doing this and it takes a long time. Phobos found out that if you use a grinding tip for a Rotary Tool its perfect for cutting out just a little bit of plastic without it drilling out the hole completely.
Why would you even care about counter sinking your motor bolts?
"There are two main reasons to do this. Firstly, if you run PEEK or RENY screws the heads can break off if they stick out of the bottom too much. Two, when you crash and your whoop lands flat on the bottom, all that force is sent directly into the motor screws and into your motor. This can lead to split bells and dropped magnets. When you counter sink your screws the plastic of the frame hits the ground first and helps distribute that force across the frame more evenly. It's always cheaper to replace a frame than a motor."
~Nightwing