I'm going to hazard a guess that those side sections mount to the interior of the vac-form helmet.
And I want to make a resounding THANK YOU for sharing all this info and pictures with us.
I'm not anywhere near rebuilding a Cylon (or scratch-building one for that matter), but its always super groovy
to see what's out there and examine how they solved problems back in 1978. Professional curiosity.
Thats a great set of pieces you got there. Treat them well. For the preservation of colonial history. : )