There's no doubt in my mind that it could produce viable offspring, after seeing what's been done (Ball X Short Tail, Woma X Ball, Carpet X Woma etc.) I don't think that a python x boa, or live bearer x egg layer more specificlly would work but that's just opinion. Only those with closed minds can't get over the first flaw in thier argument WE DON'T BREED SNAKES, we only allow animals to do what they will, and it's been proven time and again that with AND without the help of humans hybrids DO occur in the wild and in captivity. And to further that, humans are as much a part of what's "natural" as anything else...Do you think that who/whatever created all this couldn't comprehend that we would keep animals for pleasure? Or that we would travel between continents...that's pretty bold of you if you do. It all boils down to this....If it shouldn't happen.....IT WONT. There's obviously reasons human x ape hybrids aren't viable and for Donkey X Horse offspring to be sterile....those are the rules, if it can't be done than it wasn't supposed to have been...period
Of course this is all just my crazy opinion, not meant to be taken as anything but the ramblings of someone who has no formal training or schooling other than what life and my animals have taught me over the years.
If you take a step back and look at some of the rattlesnake sp./ssp. for example and how they are distributed you will see that perhaps hundreds of thousands of years ago three to four "species" of snakes are responsible for what's out there now....this is just a quick example of what I think.....take an durissus, and a horridus what what you get? Would look alot like the forms of molossus if you ask me...the range is right too. Of course this is all blind conjecture, but it's something to consider.
Or perhaps, I should get rid of all my non locale specific projects, stop thinking, read and believe only what's written and accepted and do my best, through contempt, ridicule & derision to make sure others that try realize thier obvious stupidity 
Good luck with providing the proper environment for your boas to do what they wish! 
Horridus