FWIW:
we knew how much fuel (pounds), how many people (which we multiplied by 200 pounds) and the BOW (basic operating weight of the plane). So, in our humble minds we put them all together. Then we flipped our little vspeed FLIP BOOK to the weight we came up with. We set our tri to the green band...just guessing mind you and we waited.
Across the ACARS came the W&B calculations, v speeds, trim, optional reduced power and runways.
Our flip book was already set to the right weight...it was a nice little system...(the pax times 200 took care of belly luggage)