Arched Deck Support
These pieces are bent and out of white oak.Inner Supports
The 2 arches will support the deck by the opening.
Twist...
The arch "twists" toward the bow. After measuring the old pieces this resulted in a 45 degree angle going out and a 16 degree "twist". 
Clamping Guides
The clamping guides allowed me to clamp and bend the arch on top of the deck. This way the length does not matter and working is much easier.
Steaming...
The steaming took about 3 hours. The 3/4 inch white oak bent and twisted pretty nice. Some layers separated a little but I will fill them with epoxy later.
Mounting in Place
After cutting to correct length the arch is mounted to the deck supports.
Sanded and Done
After both are mounted I sanded them into shape. Now only the bottom side has to be routered.