Yeah Jorge, you are correct....Banana kings did originate from the Long Beach-Newport phenotypes, and especially after they became more line-bred for more yellow coloration, and many times a bit less pattern too.
Hey Kevin,.....
I am sure you could find some of those floating around with dark venters, but it really depends on the individual lines that you might happen to come across. Not all of the wild populations of Long Beach-Newports from Orange and Los Angeles counties,..etc.. have solid black bellies, but many do. Just like some splendida have solid black venters, and some are more intermediately speckled.
A good indication of NLB aka "Newporter" lineage animals seems to be the strong, thick dark stripe on their tail after the the vent.
Hubbs and I saw a kid walking around Daytona in 2008 with one of these as a matter of fact, and we both stopped him and looked it over real well. It was labeled "Banana king" or "high-yellow" as I recall. But it was indeed a text-book Long Beach Newport phenotype, and of course it also had a wide dark stripe on the tail portion as well. 
~Doug
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"a snake in the grass is a GOOD thing" 
my website -serpentinespecialties.webs.com