Yea, I'm a bit worried about the length, it's a full day out, not a morning blast.
We could leave it until later in the morning, 1000 instead of 0900? Not so harsh then? Still plenty of day and time. I'm factoring the amount of time MAX is 5 hours until we hit Brighton beach. And at that point, you are no more than 2 hours from H cafe via motorways on the way home.
I'm hoping to make Box Hill a secondary meetup point for those further south to join.
EDIT: The other option for a more 'biker friendly' route with more fun roads is to skip Box Hill entirely and do the roads between Guildford and Horsham...