It would be interesting to see if there is some kind of equation that could be used to help estimate yield. Something like this - Yield in grams (Y) = Total wattage (W) x total area of plants in square feet (A) x veg time in days plus flower time in days(T1 + T2). You would need some kind of conversion factor to convert the watts x ft^2 x days to grams. The time factor is always missing when I see growers do their yield estimates.
For my set up, I typically veg the plants to about 18 inches in about 40 days, with another 70 days in flower. The plants are in 8 inch round pots, so I can fit about 40 into a 5 x 5 space. I use a 1000W light. My typical yield is about 30 grams per plant. So in my case W = 1000, A = 25, and T = 110, and Y = 1200. So the conversion factor for this set up would be 0.000436.
Plugging your numbers into the equation and solving for Y would be as follows:
Y = 800W x 16 ft^2 x 84 days x 0.000436
Y = 469 grams
I assumed you flower for about the same time as me - 10 weeks or so. Also did a guesstimate for the total wattage with a composite light system.
Would like to see some other growers use there own numbers to see if there is a fairly constant conversion factor. Obviously, there is going to be lots of variation, but it would be cool to have some idea if an equation like this could be useful.
