Fortigate Set MTU/TCP MSS for best practise NBN configuration

How to set the MTU/TCP MSS on interfaces

In order to best support VPN/SDWAN/VXLAN configurations we recommend the following settings on the WAN interface for the best experiences. 

    edit "wan1"
        set mode pppoe
        set allowaccess ping
        set type physical
        set tcp-mss 1330
        set role wan
        set username XXXXX
        set password XXXX
        set mtu-override enable
        set mtu 1492

FortiOS modifies the MSS to "$TunnelMTU - 40", so may not have to touch it for IPsec interfaces.