[WireGuard] Header / MTU sizes for Wireguard

[blurt_overkill882 at simplelogin.com]

Hello, I hope this is the right place.

I see here[1] that if you're using IPv4 exclusively, you can get away with an MTU of 1440. If my client only has IPv4 internet, however the server issues an IPv6 address for use by the client, can the client still use 1440 without fragmentation, or must the client use 1420, because even though their connection is IPv4, they are issued an IPv6 address within the tunnel?

[1] https://lists.zx2c4.com/pipermail/wireguard/2017-December/002201.html

Thanks in advance!