But, But, Lawnmower Blennies get 4-5 inches and its only a 14g and its a hex.
Not challenging you TC, but I wouldn't think that would be a good fit for that tank. Do you think it is? I can't imagine a 14g hex has much swimming room at all, especially when you get enough live rock in there. But, that is just my 2 cents!
You don't have to listen to me, but I seriously wouldn't have more than 2 fish in your tank. It won't have a lot of swimming room and though its tall, fish don't swim vertical.
2 small fish plus the CUC would stock your tank. I would stick to small fish like a Clown Goby, Tailspot or Bicolor Blenny, maybe a False Percula/Ocellaris Clown (I personally wouldn't), maybe a Cardinalfish, Hi Fin Banded Goby,...to name a few. All will need a cycled tank.