Unlike most basic pizza dough recipes, Sicilian dough recipes can have a much wider range of hydration values, from something in the 60+% range to over the 80+% range. Sometimes I can get a pretty good idea of the hydration value of a recipe just seeing the recipe and instructions and knowing what typical values are for the particular style. That allows me to be able to make a judgment as to how a volumetric amount of flour converts to a weight. This is much harder to do with a Sicilian dough because of its wider possible range of hydration values. Also, because of the high hydration of such doughs, it is common for the practitioner to add flour on the bench while mixing and kneading, and even at the time the dough is being prepped (after fermentation) to make the pizza. Such uses of bench flour will lower the nominal hydration value of the dough as calculated using conversion values for the flour called for in the recipe (5 cups in your case). How the dough is mixed and kneaded can also be a factor in how well the flour is hydrated and the extent of gluten development. For example, I know that you frequently use a bread maker to mix and knead your doughs, although you didn't indicate whether that is the machine you are now using to make your Sicilian dough and what mix/knead protocol you are using.
I played around with the Mass-Volume Conversion Calculator at http://tools.foodsim.com/
to see if I could learn anything of value. As a proxy for your Full Strength flour, I used the King Arthur bread flour (KABF), mainly because it has a protein content that is very close to that of the Full Strength flour. For the water, I assumed a value of 8.15 ounces for a cup. Technically, a cup of water weighs 8.345 ounces. However, that is based on using a measuring cup that is placed on a flat surface and where the one-cup water level marking is viewed at eye level using the lower meniscus. Since very few people measure out water that way, and typically just eyeball the one-cup marking in the cup when filling it, I tend to use a value of 8.1-8.2 ounces for conversion purposes. Often, I just use 8.15 ounces, as noted above. So, the 2 1/2 cups of water in your recipe converts to 20.375 ounces.
With respect to the flour, I used the Mass-Volume Conversion Calculator to calculate the weight of 5 cups of flour using the Textbook, Medium, Medium x 2, and Heavy flour Measurement Methods, and then calculated the hydration for the four values. I did not do a calculation for the Light flour Measurement Method because almost no one uses that method. I got the following:
Textbook: 21.932 ounces, hydration = 92.90%
Medium: 24.73 ounces, hydration = 82.39%
Medium x 2: 26.368 ounces, hydration = 77.27%
Heavy: 30.098 ounces, hydration = 67.7%
As you can see, there can be a very wide swing in flour weight and hydration values based solely on how one measures out five cups of flour (remember that the water has a fixed weight). In my experience and observation, most people tend to use either the Medium or Medium x 2 flour Measurement Methods where one dips the measuring cup into the container of flour to the point of slightly overfilling the cup, and then leveling the cup in some way, as by using the flat edge of a knife, or by shaking the measuring cup in lieu of using a straight edge. On this basis, you would use either 24.73 ounces or 26.368 ounces as the weight of flour for your purposes. In either case, you might keep track of any bench flour used and note its value so that the total formula flour can be more accurately ascertained for the next use of the recipe. As an alternative, you could average the two flour values noted above, which comes to 25.55 ounces. That yields a hydration value of 79.75%. From my reading of recipes for different Sicilian style pizzas and the results that are produced, it seems that a hydration in the 60+% range is usually too low, and that a hydration in the 85% range is too high. So, a hydration value of just under 80% seems to be in the ballpark. The true value will be lower, of course, to the extent that bench flour is used at any stage of preparing and using the dough. Also, your Full Stength flour might have slightly different weight and performance characteristics compared with the KABF that I used as a proxy for your Full Strength flour.
Whatever you do, please let us know how things turn out. I'd especially like to see if my analysis has any merit, whether you decide that I am entitled to another star or not.