has anyone had success in using the cove as their primary source of gold income?
I have; in fact that is how I started to have more success in the game. Two engineers and skilled traders @ 250g and a cannon foundry for the cove rakes the gold in (cannons require iron and wood). Perhaps a blacksmithy (cutlasses) to convert the remaining iron into money. I try to max out on those skilled
captives before the gold first runs out.
The cannon foundry can hold relatively large quantities in its input so its hauler can be regularly fired to haul somewhere else.
Then I use some cutlasses on my ships, buy muskets from the blackmarket, and capture cannons.
Eventually I sell other items through the cove, and get rich enough to be able to buy education, larger ships, donate money to pirates, invest in wealthy captives stuff, risk more piracy.
And the Severous-type convoys are useful when the cove hauler decides to spend time on hauling (low profit-per-load) beer in.