I built the extension and a mini outfeed table today. I used all left over ply and hardboard and finished it off with a few coats of poly.
I built the mini outfeed table so that the fence has a consistent surface to run across from right to left. Without this, it would ride on cast iron and hardboard; now it just rides on hardboard.
The outfeed table that I am building will be on casters and will latch onto the mini outfeed table with some rubber latches.