Me and David123 completed this fun 5 mega 2.5 v us 2 on the map fiveonthree, with both of us playing romans.
>Results!<The key to this was simply using all the resources we had at our disposal to produce as many units as possible. Also, we took particular roles during the game e.g. I took all the most dangerous gold spots, while david123 ordered commands for our army (n.b. There were no shared resources. David123 simply told me when to retreat and attack).
Romans is also a good faction to choose for this battle, as it allows you to generate a large army very fast. Romans is quite resource-intensive, but this map has plenty of gold and wood to counteract this weakness.