When I edit connections in a controller, even non-gasses, I get kicked from my server. Another person found it didn't happen in single-player. The log complains about a large packet being, my guess is from the client-side screen to the server. This was originally reported to the XNet issue tracker, but we found that it didn't happen without XNet Gasses installed. My specific actions were to create a network channel, create a connection, and enter a value (1 to be precise) into the "maximum items in inventory" box. It didn't kick me until that last step.

Here's what the log said:
[25Feb2021 18:49:52.356] [Server thread/INFO] [net.minecraft.network.play.ServerPlayNetHandler/]: Dunkmania101 lost connection: Internal Exception: io.netty.handler.codec.DecoderException: java.io.IOException: Payload may not be larger than 32767 bytes