Thanks for pointing me to tha Grow Bible, man! I have this figured out now:
the only way to determine if the genes for 'big' and 'potent' are dominant or codominant is to breed it with a plant that is small and weak. This would be a BB x bb or Bb x bb cross. the BBxbb would result in 4 plants that would resemble the dominant parent, 100% big plants, while a Bb x bb cross would result in offspring that resemble the recessive parent in 50% of the offspring.
So - I was given a free seed with my order, it's both smaller and less potent than either of my intended parents, SOOOOO.... if I create a cross by polinating that free seed with my f<m plant (which I intended to already), and the offspring 100% resemble the f<m, I know that 'big' and 'potent' are dominant. If they resemble the free seed, the genes for 'big' and 'potent' are codominant!
Technically there is no real way to know until the next generation, I guess, but man, a lot a really good applied information in that article, put together in an easily read format reps to Green!
I already have a very strong feeling that I will be getting exactly what I am trying to breed, which just a slight variation on two very similar parents, very similar to both - I really enjoy the direction that these forums sends me, I always end up glomming a massive amount of information when I put any question to the group!