My students are also waiting on clarifications. I see one major clarification needed in regards to energy transfers.
One could interpret energy transfer in two ways. First, that to be a scoreable energy transfer one must actually convert joules of energy from one form to another. With the term "Energy Transfer" used so much in the rules I could easily see this interpretation being used at our regional unless things are clarified further. Alternatively, one could interpret a transfer as transferring the "signal" (chain of events) from one basic energy from to another. Mandating that a quantity of energy be transferred makes this event much harder, but not impossible. It does not limit one to the energy of the starting event as some have suggested because one can always add non-scoring steps that add more energy between the scoring steps. For instance, an electrical switch would not score as Mech -> Elec. under the first system because none of the mechanical energy that enters the switch leaves as electrical energy, but it still could be used to switch on a motor that converts electrical to mechanical. Similarly, uncovering a light source would not transfer Mech -> Light, but a solar cell could then covert light to electricity. Under the second interpretation all of these would be valid transfers. Hopefully we will soon see this clarified. I suspect the soon-to-be-posted ETL will use transfers that would not be valid under the first interpretation, but I could certainly be wrong.
On the other longstanding debate. I think homemade batteries will be allowed via a FAQ, but until then they could be disqualified. I also would not count a commercial battery as Chem -> Elec not because it is not student made, but because prior to the start of the event the battery already had a voltage difference between the poles which represents a preexisting electrical potential. To count as Chem -> Elec in my book one would need to assemble the battery during the run, so a new electrical potential is created. In other words, to count as Chem to Elec. one must alter the chemistry on the input side.
The "black box" rule in my book only states that all transfers must be visible (as stated in the rules). To extend it beyond this would be reading something into the rules that just doesn't seem to be written there. That said, this is at the discretion of the event supervisor so I would check with them prior to each competition whenever possible.