ANSWER: You are mixing two different usages of the term "heavy" carrier. Anything that counts as a CVA for production must be built in the shipyard. Medium carriers which can be or must be escorted as heavy carriers are still produced as medium carriers and can be produced outside of the shipyard.

QUESTION: Can Division Control Ships (toothless cruiser hulls which have both PFs and fighters) be built by overproduction?

ANSWER: They are cruisers (which can be) and fighters with less than eight factors (which can be) so they can be.

QUESTION: Rule (431.33) says that the Federation CVB cannot be overbuilt, but rule (432.5) says that the surcharge is not doubled if it is overbuilt. Huh?

ANSWER: This is just a glitch. As the CVB cannot be overbuilt, the note in (432.5) is effectively meaningless.