c/b and s/b rods cross breed.

[usngsm2]

When is a c/b rod used as a s/b rod or do you not cross apply them?
My question is derived from the fact that one tournament I was asking about had a limit to the non-boater of 7 rods max. If you are like me, at least one is a spinning set up the others or c/b, s/b, tw, worm, flipping, frog and wieghtless. When I am selecting my c/b rod it's the 5.1:1 curado D on a crucial c/b rod and my s/b is a curado D 7.1:1 on a g-loomis s/b rod. Now depending on what the fish are doing I some times throw a small s/b on my c/b rod. But never the opposite, I don't know why just never did.
I want to know what application specific rods do you have that you sometimes go to another technique with and have you ever done anything like the afore mention? Do you look for the same things more or less in a c/b rod that you do in a s/b rod? And with the exception of technique specific rods what is the over all difference in the two?