When im piloting a spire i tend to have me piloting (dur), an engineer up top on the front facing gun (howitzer for me), a gunner on the big main gun at the bottom (heavy mortar for me) and an engineer on the 2nd side gun at the bottom (chain gun usually). If the main gun is disabled and theres no time to repair i get the gunner to get up on the top right gun- i tend to like to keep at least 1 gun firing on the enemy. I take a ranged tactic when playing as spire so usually i can have all crew members on the guns.
When facing forwards to fire your guns you want to get as many facing the enemy as possible and able to fire so if for example you have 2 people on the front facing guns and someone on the top right gun you want to tilt your ship about 20 degrees to the left (I think) so that right side gun can fire but your forward facing guns have range at the same time.
When under fire I get the engi on the bottom floor to stay on the hull and if needed the top engineer will go to repair the main engine and balloon. When things get serious engineers on full repair with the gunner roaming around.
My usual pilot gear is Impact bumpers, phoenix claw and either nitro or moonshine (I've started liking moonshine quite a bit but it needs good communication with the engis) Sometimes with the Spire though i'll replace the impact bumpers with hydrogen (As the spire is pretty weak anyway). If im being pursued or a ship is charging a quick burst of hydrogen in the balloons and putting the engines on full forward (With a burst of moonshine if i can afford it) then a quick spin and full reverse on the engines once halfway turned will usually get you behind the enemy (Get the engines!) with your guns facing them, if taken heavy damage then it also gives some breathing time to repair.
One problem is that if you don't communicate what you're about to do with your team or if you've never flown with them before and they don't know your flying style it can catch them by surprise and you might just end up with no engines and a wrecked balloon (Remember hydrogen stays on for 5 seconds after you deactivate it, like impact bumpers.)
I have a feeling i didnt explain the above properly so i'll sum it up here
Pursued / charging enemy
full reversing (warn crew about what you're about to do next)
when they get around 350m (bit more than Flamethrower range, guessing time!) engines full forward (use a boost if you need) , activate hydrogen
deactivate hydrogen quickly afterwards and spin the ship around
when ship halfway spun put engines on reverse again and get people on the guns
fire away at the engines to disable them
shoot them some more and hope no one ambushes you
Well anyway that's just some spire stuff
-edit- oh one more note since i have a heavy mortar on front i can usually disable a balloon and circle around / follow them to the ground without getting to close and keeping their balloon disabled
-edit2- huh i didnt realise i wrote so much xD tell me if i;m rambling on to much