Holes are ofcourse for cooling, but also to easy up the assembly.
Grooves/slots are dimensioned so that it "locks" the hubcap in place. You need about 10 kg of pulling force to remove hubcap in wrong way. If you do it rigth the force is about 2 kg
.
The whole cap is measured so that it makes similar round shape that mooneys have.
So in short everything has a purpose and some shapes even many purposes.
I would like to start help selling those in the states also, but someone needs to start his own company/business there. I can assist the manufacturing/tooling etc but the selling needs to be done by someone else...
Do the rims look similar in the states?
Is the 22.5" size the most common?