How much is too much?
Basically, it is a balance. If you are taking too much damage in battles, you have too little.
If you have no space left for weapons, you have too much.
I've had ships with 4000 front shields. But, that was with level 32 shields. The better measure is the amount of KT you have assigned to shields and armour.
I have started reducing my armour. I am more interested in the added property of the armour type than the weight of armour. So I tend to balance more towards the shield than the armour. Then boost my shield recharge rate.
My Terran carrier has 120 kt front shields, 60kt side and 40kt back. Sometimes I shift a little more to the back.
I have 2x10kt front armour, 5 & 10kt side and back armour. Split between stealth and emissive. Remember that 2x5kt emissive gives twice the added damage resistance than 1 10kt emissive. The bonus is independant of size of component, but depends on the number of components.
The emissive really cuts down on the damage you take from hits. The stealth may be a waste of time. (I should do some tests...)
Two maneuvering thrusters and two afterburners compensate quite nicely for the slowwww turning rate of the carrier. Now, if there was just some way to raise the top speed of the ship...
(Yes, I could mod.)