For compactness, there are several options for a stock that are definitely legal without any grey or debatable areas:
[url=http://www.defensive-edge.net/tacticalstore.html]Sully Stock[/url]The Sully Stock is the smae length as a collapsible stock open to the first notch, which is halfway open on a four or three position stock. This stock length, IMHO, is the perfect length for any situation. It is versatile enough to be used with light clothing or heavy clothing. The shorter the useable length of pull, the faster the weapon is to get on target and the easier it is to stabilize the weapon. The sully stock is at the lenght that is, in my expereience, the best useable lenght of the stock no matter what gear or clothing I have on.
[url=http://ar15.com/forums/topic.html?b=7&f=22&t=173414&w=searchPop]ROCK RIVER ARMS L.E. ENTRY TACTICAL BUTTSTOCK KIT WITH KNIGHT'S ONE INCH STOCK EXTENSION SLING MOUNT [/url] This is abpout the same size as the sully stock. The stock can be used by itself, and is about the same length as a collapsible stock in the fully closed position. The stock can also be purchased without the spacer at [url=http://ar15sales.com/rraparts.htm#parts]Legal Transfers[/url] or [url=http://www.adcofirearms.com/rockriver/rockriver.cfm?page=rra]Adco[/url]
[url=http://ar15.com/forums/topic.html?b=7&f=22&t=167618&w=searchPop]ARFX-E stocks[/url] This is about the same length as the RRA stock, and it has the option of a half inch or one inch spacer/buttpad for added length.
I am sure there are other options as well, but these are the most popular. Hope these help until the ban sunsets.