Worked left wing details by fitting filler and drain provisions along with initial lower stiffener fabrication. There are quite a few stiffeners (23 per tank). As near as I can tell, this was a later design modification since the stiffeners are not apparent on any of Dick's prototype pictures I reviewed. Stiffeners on the bottom of the tank seem like a good idea to maintain the tank shape with a fuel load. Other plans I looked at all seem to have them. I estimate that it adds about a pound of empty weight per tank and a reduction of about .25 gallons of fuel.