Well, from cutaway's response I understand (and correct me if I'm wrong) that while "up" and "down" work against one another, both "up and down" work together against the throttle or third line? that would explain what the third line is pulling against...

But now, going back to Brodak's large selection of 3-line bellcranks, apart form the actual size, what are the differences?
I mean - some say they are for an inverted engine and some for an upright one, but if I use a flexible throttle cable - what does it matter?
Also - some say the "up" line is the front one and not the back - what is the significance of this?
And finlly, how effective is this 3-line throttle control during taxi? (is it really possible to taxi the model around the circle reliably?)

Sorry for so many questions...but I don't know anyone who flys this type of model...