Here are some of my thoughts on the Hebrew dagesh:
1. The dagesh "forte" appears after patax, xirik, qubuc, (segol). In
my opinion, it preceded the NIKUD, and served to provide hints as to
the proper reading of the consonantal text. It has nothing to do with
"gemination".
Examples:
אַקּוֹ, גִּבֵּן, חֻפָּה
2. The dagesh forte is not placed in the letters אהחרע nor in a
letter marked by Schwa. in the latter case it is transported forward
to become the dagesh lene.
3. Because it is otherwise redundant, the moved dagesh is kept only
in the influenced בגדכפת letters.
Examples: