Looks like only 48" at the stern towards the bow.  I worry about creating a hook in the hull if the 2x6 deflects.

Getting contact with the hull the entire length?

You could glue and screw another identical board on top to stiffen it up a bit, if it doesn't mess up any alignment, but a 2x6 should be OK.

I'm not a Structural Engineer but it meets my TLAR (That Looks About Right) standard. 

Boards have been narrowed down to approx. 5" They are currently 48" in length. The bracket is approx. 13 1/4" in length so that gives approx. 17 1/4" hanging beyond the support of the bracket. Is that to much? Looking for opinions.

Here's what I have decided to do for the bunks. These brackets were for a later trailer and held three rollers. My son cut down the sides eliminating the holes for the rollers. The sides needed to be cut down as they were taller than the 2" x 6" The
2" x 6" also needed to be cut narrower to hold the board. These brackets are approx. 13 1/2" long. My questions is how long should I make the 2" x 6" ? It will be pressure treated wood and covered with bunk carpet.

Mike,

Congrats on the award. Beautiful job on the trailer.

Congratulations Mike... Looks awesome!

Congrats Mike! First place and still not finished!!. That's one nice trailer for sure.

Beautiful Mike.