Here are two pics of the inside of the oven, and a quick sketch that shows how it works. It isn't a traditional dome really, the top is fluted to promote secondary combustion during the burn, to make it more efficient and extract more btu's out of wood. I suspect this isn't the ideal oven shape however.
Looking at these pictures, it seems like the proportions of this oven are off, compared to a traditional pizza oven, it seems too tall instead of wide and relatively flat like a real pizza oven.
After reading around this forum some, I'm thinking that the top is just too far away from the pizza, so I could either raise the deck some, OR add a top stone? It seems like that has worked well for others, and if I got something slightly more conductive than fire brick (which the deck is made out of) like soapstone, it might help. I could probably set a slab up on a row of fire bricks, so it would be 2-3" above the top of the pizza.....it would be hot though, like 700-800 degrees, so maybe it would want to be higher? Thoughts?