I'm playing with PR's Ciabatta formula (BBA) today, and I know you guys can save me considerable trial and error, so I hope to take advantage of the vast knowledge and experience in this group.  I plan to do the formula three times to compare all aspects of the bread, such as taste,  texture, feel, time involved and probably some I am not aware of yet.

First, I'll make it as writ using the biga.  Then I want to use sourdough (my barm is ready) with the added dry yeast, and finally, with only sourdough to leven.  Of course I have no idea as to the amounts of barm to use in the last two mixes. 

When using the barm and the yeast, would I use the same amount, by weight, as the biga?

I'm going back to read PR's BBA info about fermenting and sd, hoping he tells how to substitute one for the other, and I just forgot, but I would love to hear what our resident experts (or not) think about it.  Everyone here is so helpful, and I could read you on and on, and I do.

Syb