The screw for this are all wrong! I have nylon screws and washers that will work, but I have to make the case holes larger to accommodate the nylon screws diameter which can be tricky, unless you have a drill press to keep it centered correctly. My recommendation, don't buy this unless HK updates the product with the correct parts and hole sizes or be willing to make to correct modifications yourself.
i strongly recommend to get this Mounting Box this box protect the HKPilot Mega V2.5 Flight Controller
from vibrations , when landing your RC and the worst case is Crash! since this broad has sensitive parts in
Joining each section required a tap with a soft faced hammer, very close tolerances, however this makes for a tight glueless assembly. I still added some foam to help shield the baro sensor and all works well in this case.