I learned this week that 80/20 extrusion is made to interlock, by putting the edge of one piece into the slot of another piece. I believe Cybersonics (103) used this in 2004 and 2005.
http://www.cybersonics.org/Cybersoni...2005/tower.asp
When the extrusion is interlocked that way, there's a lot of sideways play that would make a slide impossible, so you would need to have two parallel, linked sets of extrusion.