5 is enough? Hell, it's not enough for me even for vanilla ship. Well, it's fine for a few smaller ones.
I mean, one CAN work with just 5, but it's so grossly inefficient - even moreso with mods.
Consider this - a cruiser with several front missiles, left big guns, right big guns, left PD guns, right PD guns, rear PD guns and centerline/front guns. There is NO WAY you can effectively use that.
You either have to group PD into one group (thus limiting your PD to attacking just one target at a time and only on one side) or group you biggr guns with the same problem.
If the target is to your left, you right guns are going to do nothing even if there are targets there.
Now if you have multiple missile slots it gets even worse, since missiles are something you want to have control over. You can forget about having different missile types, since there aren't enough groups to fire them separately, and firing a slave of different missiles for different roles is a waste, so everyone always just uses 1 type of missiles.