Do all or any A6M’s have lightening holes in the seats? If so, how many and where? Thanks for any information.
Boy, I’m chatty today. I may be corrected on this, but every one I’ve seen in museums or photos have lightening holes. On many kits, these are represented and you need to simply open them up. If not, find a reference and make them with your pin vise. And bevel the slightly. It really adds a lot to the cockpit without much effort. However, no one can make blanket statements about Japanese a/c in the latter part of the war. They made do with anything they had, and tended to simplify everything. But on the earlier A6Ms, you’ll have the holes in the seat back.
Here’s a pic of the seat from my Trumpeter 1/24 Rufe. The Rufe was the seaplane version of the Zeke, manufactured by Nakajima. The color is Nakajima cockpit color. The seats in both aircraft are the same.

Hope this helps.