IPsec MSS clamping value shared for IPv4 and IPv6
MSS clamping for IPsec can only be set globally. As a result, a value of 1452 for an IPv4 tunnel (required due to my pppoe WAN) is not suitable for an IPv6 tunnel. The latter in my case requires an IPsec MSS clamping value of 1346 for IPv6 web sites accessed across the tunnel to load.
Separate MSS clamping options in the GUI would allow more efficient use of IPv4 tunnels when IPv6 tunnels are also present.