Hi,
the mission is not that difficult than it seems. It could be solved without cheating.
Here how it worked for me on normal difficulty:
At first make two groups. The Elcos as one and the G5 rockets as the other.
Let the Elcos go straight to the isle, moving in from the south not too fast. The G5s make a wide circle to the west around the isle and move in from the north west, let them stop about 2 miles (2 squares on map) away from the base.
When the Elcos spot the first enemy boat let them form in line and go wide circles as the fire (it's better to support the crews by manual firing) on the enemy. Don't let the enemy boats come too close, fire on distance. When too ore more enemy boats appear, lay some smoke to seperate them and take them down. They don't need much hits but are dangerous when they come close. So don't let them...
When the enemy boats are sunk, select the tactical map, select both G5 and switch to "attack with rockets". Go near to the isle for about 1,5 miles and select the base as target. The Rocket boats will attack now, they aim very good (i tried to fire the rockets for four or five times manually and did not get a direct hit). Maybe you will try to fire yourself, but when you want to solve this mission quickly, the crew does very well.
After destroying the base, get all boats together and move to the south just were you came from. That's it!
Regards, midnite1977