Hi Marc,
Thank you for your detailed response and the list of aircraft/links. There are some very nice photos showing the battery installation.
Regarding your comments about photo 2.: I fully agree, the Type 041 engine cowling was also employed in Mtt produced G-14/AS. Another good example of a Mtt G-14/AS with two oil filler holes is the aircraft at Falconara (see photo at your Flickr album:
https://www.flickr.com/photos/280920...57635159457168).
I am going to publish photos of brand new G-14/AS at a forrest assembly line that also featured the Type 041 cowling. There is not yet any battery installed, but it may well be that the aircraft was not yet fully assembled and the battery was still missing (also the compartment door was not yet in place).
Cheers,
Roger