If you enter a vehicle and your soldier models helmet comes into view blocking it, then you have problem with the hlava and/or mireni selections.
To fix this problem using the hlava, first zoom into the view the head of the soldier model.
image 1 here
As we see we have the helmet, face/head of the soldier and then even the “bandanna” raghead shit on this guys head. So everything must be selected so they are not getting into a view during vehicle transport.
image 2 here
Like this, now all of the head is selected. Now simply go to the hlava selection and right mouse click and select Redefine.
image 3 redefine here
As you see here.
Do the same for mireni selection just in case, actually I’m not 100% sure which one causes it, I bet hlava, but better to be sure.
Also if you binarize the MLOD model and it throws you a helmet/hat/eyelids visible inside a vehicle, it means you must make config.cpp with proper CfgModels inside the binarized directory. If you fail to binarize with the cpp, the helmet is visible.