Looks good, as of recently my engineer goby is no longer in my tank, but he was approaching a foot. He would build 8" mounds of sand and kill my bioload by stirring up way too much (I didn't plan ahead and eggcrate the bottom at all.
But here's a pic from the gift shop at baltimore aquarium, they have 10-12 huge engineer gobies. Theyre approaching 16" and theyre fat too.
(crappy pic since I had to lean over the cash register to get a quick pic of the tank behind the counter. cashier thought i was nuts)