My set up is like this:
Artemis - Mortar - Merc - Mortar - Artemis
Ideally the top gunner is a buffgineer who buffs hull, main engine, and their gun. From range I use Artemis going in, then switch to mortars as they come into firing range. Each side engi is on one engine and either balloon or hull, but we don't really look to repair while the enemy is still alive.
Double mortars spewing forth like a fountain of death on the enemy ship is one of the more glorious things I've seen in this game.
I love my Mobie -- Long Live A Love Supreme.