Darren,
You have to be mighty careful when selling any stain guarding product, even conventional ones, as they do have limitations and if it doesn't do what you said it would your reputation could be shot. Even conventional stain guarding products can leave customers expecting their carpets are fully protected from stains when nothing could be further from the truth, so you e got to be really careful about how you sell it. If you're mixing SPM with dynamall you could well be undermining its stain blocking properties as the addition of another chemical changes the properties of both and leaves you with an unknown quantity.
Simon