I am not expert on Boa localities. I work with a small group mainly for their genetics and appearance. I love boas of all sorts!
Here is a good link to Longicaudas:
http://www.riobravoreptiles.com/boas_long.htm
Wade had or still has Hog Islands.
IF that was what a breeder had on his table, then most likely he knows what he had. Why he chose to cross breed, I have no idea.
You could go to a 10 day feed schedule. I do the 10 to 15 days for the ones that are over two years old and doing good. My older girl, 8yrs+ and over 6 ft and about 25lbs, eats once every 3 weeks and is doing great. She eats once a month between December and February. She is doing great!
My male possible Super Salmon, has the same small head but that is just how that line is. He eats on the 15 day schedule for the most part.
So how old is this boa?
How often are you feeding him and what are you feeding him?
I have a good boa breeder friend and he only feeds his breeding females more often before breeding season and after they give birth. If you need more help, I am sure I can get you more information. But it looks like you are doing good by Gauge so far!
And yes, you do not want a fat boa...it will shorten his life span. They dont eat like corns at all!! Yet, they will if you offer it to them.