Best MTU for L2TPv3 mode with kernel offload?

[stevefan1999-personal]

If my calculations are correct, this is the best base MTU: Visual packet size calculator — Daniil Baturin

If I want to add batman futher, I have to add another ethernet frame and IP on top of it, so the new MTU would be like this: Visual packet size calculator — Daniil Baturin

I'm not sure if I made the calculations wrong