Gossip max_message_size does not account for overhead

[link2xt]

I have set max_message_size to 128 * 1024, but was only able to send 128 * 1024 - 90 bytes of payload.

Doesn't the setting introduced in #2340 control the maximum payload size?

As a workaround I am going to test that I can send 128 * 1000 while setting the limit to 128 * 1024, but this does not seem very robust: deltachat/deltachat-core-rust#6105
Is there any upper limit on the overhead?

Ideally the setting should control the size of the payload and iroh should add maximum overhead size internall IMO.