The flanged hex head fasteners work well here.
A few small printed part changes would make it perfect:
- recess for screw washer needs to be wider since the flange of the bolt is wider than a washer
- the top rear fastener needs more clearance for the wrench
We can also get an 8mm crow's foot for a torque wrench and actually (for the first time) be able to torque these fasteners to the spec and check them :-O