'42 works. Are you sure you wanna do 400? The stacking limit changes to 3 ships / 5 planes at 500, not 400. But it's up to you!
I like the idea of the increased stacking limit, but I dont think the rules are well tested for it. For example: under standard limits, you can have two Atlanta CLs in a sector, making four 8 dice AA attacks. In 5pp pt. games, you could have three of them making six attacks, exceeding the plane stacking limit. Let me know if I've missed something.