Answer:
"silly person windows can be any size
they are usually H4' x W2.75'"
This is in fact not true, so the answerer is the silly person. If a windrow is too large, then it becomes anoxic at a greater rate than one would be able to turn is, or if your a commercial composter, it won't be cost effective. If however the size of your newly formed windrow is too small, the loss of moisture and volatile substances can decrease your organic matter ratio. This will lead to piles that could vanish completely...
For more info, please visit:
http://www.jstor.org/stable/25042565
http://www.omafra.gov.on.ca/english/engineer/facts/05-023.htm
http://books.google.co.za/books?id=H1CAb3Nx35wC&pg=PA401&lpg=PA401&dq=Windrow+dimensions&source=bl&ots=_XLLh_VkVz&sig=7Mx5oyDUWi74DvNmq-lNuiYbWto&hl=en&ei=xFOZS4mcBsuC4Qbu1Yz7Cg&sa=X&oi=book_result&ct=result&resnum=12&ved=0CD8Q6AEwCw#v=onepage&q=Windrow%20dimensions&f=false