I currently have the following fish in my 65 tall.
Yellow Watchman
Orange Spotted Goby
Sunburst Anthias
Canary Blenny
2x Bangai Cardinals
Green Mandarin
Everyone is peaceful to each other and are doing great as far as I know. The mandarin is fat and happy and there are tons of pods exploding in growth all over the place. The two gobies are so cool, they swim along side each other, they lay right nexty to each other and even rest together side by side at night. I thought the Yellow Watchman would have attacked or bully the Orange Spot but it was friendship at first sight. The only "problem" I can see is the Sunburst Anthias might not be getting enough to eat as the 2 Banggai Cardinals out compete him when the mysis shrimps are flying by. He gets them, just not nearly as much as the Cardinals.
I think the last additions I will add will include
2 Onyx clowns as soon as I can find them...oh and maybe a Solar Wrasse.
In terms of being overstocked, I think I still have some room considering these fish probably poop less combined compared to a single tang. I will also assume that the O2 intake of these little guys is also less of a 3 inch tang of any kind. The only problem I can see in terms of being overstocked is the amount of territory. I think I have a fairly unique aquascape and can provide enough room for them. Not to mention that two gobies share a territory, my canary blenny goes to rest on the hanging attachment of my Seio.
I think if you stock with less aggressive fish, you'll be fine. Oh forgot to add, every single coral I have is showing full polyp extension including my 3 inch Crocea clam.