I agree, mixing BCC with anything only improves the looks of the other animals involved (bci, bco, etc.), it always makes an animal that's uglier than the original BCC. Using a BCC in a project is essentially a shortcut to years and generations of selective breeding. And honestly, the goal of using them is to create an animal that looks nothing like the original animal (bci, bco, etc.) that it was paired with (ie, bci's with REALLY red tails).
As for Suriname X Guyana locality crosses. Yes. It happens. A LOT. It happens knowingly, and unknowingly. For many years (and probably still today), many importers separated their shipments from Suriname and Guyana by attaching a label of "Suriname" to the "pretty ones" (and/or pink boas) and a label of "Guyana" to the "ugly ones" (and/or purple boas). Those importers, and others will also happily sell you whatever you're looking for (if they just got a shipment of Surinamese BCC and you call up looking for Guyanese BCC, GUESS WHAT SHIPMENT THEY JUST GOT IN!!!?? lol Even guys with great reputations in this business will do that). So, because of the relabeling, many people have a Guyanese BCC and think they have a Surinamese BCC, and vice versa. So, when they breed that animal, they are often unknowingly crossing the two localities.
There are also people who truly do have a Surinamese and a Guyanese BCC and intentionally breed them together. I see nothing wrong with this as long as they are advertised as either Suriname X Guyana, or, Guyana Shield BCC as both labels are correct. To call them one or the other is dishonest. I do not breed Surinamese to Guyanese for many reasons, one of which is that I don't have any Surinamese (any more).
Finally, there are other people who buy a boa that is legitimately from Guyana, and then when it arrives in their collection, they arbitrarily begin telling people it's a Suriname. I'm not aware of this situation happening in reverse (Surinamese magically becoming Guyanese) as I think this goes back to my second paragraph about "ugly ones" and "pretty ones" and the consequences of the Guyana label becoming less desirable.
How's that for a short answer? lol 
jb
PS, here's my favorite Guyanese boa. Notice she's pretty and pink - not like some dishonest importers would have you believe these boas are.

She was a little over 2 in this picture and has since gone on to give me two litters of BEAUTIFUL Guyanese BCC and is gravid again
She's 9 years old now 
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What's written above is purely my opinion. In fact, MOST of what you read on the internet is someone's opinion. Don't take it too seriously 
Jonathan Brady
DeviantConstrictors.com
Deviant Constrictors picturetrail
