I am putting in a new silage pad.  I am wanting to try a flat drive over pad so I can pack it both ways, or I could use it in the future if I switch to bags, or put a building on it.  I got a quote for standup bunker walls delivered and set and it was almost $40,000.00 for a 150 ft long pad, so that factors in as well. 

My old pit silo holds about 1200 tons and it is 60 by 100.  There are times of the year when I am trying to use up wet wrapped hay that I do not feed it fast enough to keep the face fresh, so I would like to pour a longer and narrower pad, like a 30ft or 40ft wide by 150ft long. Is that too narrow to get any kind of height to the pile?  What is estimated tonnage for a pad that size?  My calculator only shows tonnage with bunker walls.

Local rebar supplier has epoxy coated rebar and recommends it for silage acid over time.  Is that worthwhile to spend the extra money for it in a silage pad?