Itís difficult to give a specific answer to your basic question on the knead time because it not only depends on the dough formulation (especially the amounts of flour and water), but also on the size of your processor bowl, the size of the dough batch, and the speed(s) used and their duration(s). I believe the common bowl sizes for the Cuisinart food processor for dough making purposes are 11 cups and 14 cups, and the speed choices are off, on (one speed only) and pulse. Some of the newer Cuisinart units also have a special dough cycle, which can also alter the required or desired knead times.
You indicated the dough formulation you have been using and it appears that it should work without any problem in a Cuisinart processor having the features mentioned above. However, since you specified the flour by volume (and possibly also the water), it is hard to tell the actual hydration you have been using. I donít have any All Trumps flour on hand but I do have the comparable Sir Lancelot high-gluten flour and two cups of that flour measured out by volume textbook style comes to about 9 ounces. If you are using 6.5 ounces of water, by weight, the hydration comes to a bit over 72%, which would be a wet dough to use a food processor to process. However, one of the nice things about a food processor when used to make pizza dough, is that it is easy to balance out the flour and water ratio by adding either more flour or more water until the dough comes together around the blade as a unitary ball. In my experience, when that condition is achieved, the additional knead time required is usually less than 20 seconds, and more typically, 10-15 seconds. Quite often, I only use the pulse feature.
If I were making a very low hydration dough requiring a long knead time, such as a cracker-style dough, then I would use a longer knead time. However, since your dough appears to be a high hydration dough, I donít think you will need more than 10-15 seconds knead time for your dough batch size (I estimate about 16 ounces). If you use much longer than that, you increase the risk of overkneading the dough and also significantly increasing the temperature of the finished dough. It is possible to kill a dough using a food processor but you would have to run the processor at full speed for several minutes. Itís an intstructive and fun thing to try sometime.
Maybe you have already seen the following posts as a result of searches you apparently conducted, but they may be helpful to the extent that they are directed to pizza doughs made using a food processor, in my case, a Cuisinart 14-cup food processor:http://www.pizzamaking.com/forum/index.php/topic,2189.msg19289.html#msg19289
(Reply 31). As you will note from the above posts, the key factor to control when using a food processor to make pizza dough is temperature. Also, the sequencing of ingredients is an important consideration when using a standard Cuisinart processor.