MTU on OSPF6 - Feature request

In OSPF we are able to set the MTU on a point-to-point neighbor to overcome MTU differences between sites.

In OSPF6 this is not possible.

This means we cannot use OSPF6 between sites with different MTU requirements. And recently we upgraded some sites to 5.2 or newer while some sites remain at 5.0 for now. We do not have OSPF6 between these sites now because of the new MTU algoritme in 5.2 and newer.

It is really important that we are able to set the MTU on OSPF6 interfaces. Or is there an alternative? We tried setting the MTU on the interfaces, and on the IPSEC tunnels but it didn't resolve this.