I just weighed it now that its got a few coats of Butyrate on all the panels -- 11.5oz. Not too outlandish I guess, but a bit on the plump side.

When I was building the I-beam I didn't have any 1/16 ply on hand and used 1/8 instead. That cost some and I widened up the center ribs to get more gluing area which cost some too.