In the version of the Lehmann dough formulation I gave in Reply 111, the amount of preferment can be stated in three different ways: with respect to the weight of the Total Formula flour, the weight of the Total Formula water or the total dough weight. On this basis, the percents are 14.39%, 23.59%
, and 8.84%, respectively. The number I highlighted, 23.59%, is the number you asked about. If I used say, 8 ounces of natural preferment instead of 9 ounces, the corresponding numbers would be 12.76%, 20.92%, and 7.84%, respectively. It is important to keep in mind that when I came up with the dough formulation at Reply 111, I was only trying to come up with a formulation that might mimic your existing Lehmann dough formulation in as many ways as possible. I was not trying to come up with a dough formulation that could be used to make a dough that could be fermented solely at ambient temperature. I know that that wouldn't work for the time that might apply in your case. I was contemplating a fermentation protocol that would include a period of room temperature fermentation, a period of cold fermentation, and a final temper at ambient temperature (such as would prevail at market).
I should also note that there are members who make only room temperature fermented doughs (or doughs whose temperature is controlled by a unit such as the MR-138), but there are also many members who use natural preferments in quantities greater than 5% of the Total Formula water (or the equivalent as a percent of Total Formula flour or total dough weight). Marco was trying to use his natural starter (Crisceto) in amounts that would provide leavening only, not in preferment quantities that might produce acid levels that would affect extensibility, result in an overly crispy crust, affect the flavor profile in some unwanted way, etc. That was just his approach. Some people use it implicitly, others don't.
If you want to make an ambient temperature fermented dough only, you would perhaps want to take a look at a dough formulation such as given at Reply 3 at http://www.pizzamaking.com/forum/index.php/topic,1415.msg12892.html#msg12892
. In that dough formulation, the amount of starter comes to 5% of the formula water. However, even if you use less starter than 5% of the formula water, I have doubts about your being able to have dough balls on Friday last until Tuesday at your prevailing ambient temperatures this time of year. I say this based on my experience making dough with no yeast whatsoever other than the wild yeast in the air and/or in the flour. If you read Reply 84 at http://www.pizzamaking.com/forum/index.php/topic,7225.msg78779.html#msg78779
, you will see that even with no yeast added to the dough ingredients, it will be difficult to get beyond about 30 hours at a room temperature of around 82 degrees F. You would have to use cold fermentation somewhere.
I have always viewed what you want to do as a logistics problem, particularly if you are thinking of making and using naturally-leavened dough at market one day a week. Making a single dough ball and pizza with natural leavening successfully using only ambient temperature fermentation does not do you much good if it can't be translated to a one-day-a-week use at market. You have to marry the dough formulation with the fermentation protocol and do so within the strictures imposed upon you by the folks who manage the market and by the regulators who monitor activity at the market. For example, it might not be permitted to bulk rise the dough or do the dough division outside of the market, for example, at your home. You would perhaps have to get some dispensation from the usual rules.