Setting MTU on ethernet bridge with netplan

Background: I decided my home Linux server had been through too many LTS upgrades, and did a fresh install of Ubuntu Server 18.04. The old /etc/network/interfaces.d system has been replaced by netplan and networkd. I was able to configure a bridge device and attach ethernet devices, but setting the MTU doesn't work. (I have the MTU configured in netplan for both the ethernet device and the bridge device) I managed to hack in a workaround by making a networkd-dispatcher script (routable.d) that calls `ip link set mtu ...`, but wondered if there's a proper way to make this work on netplan? Cheers Toby