inch and 5/8 strut. http://www.unistrut.com/Browse/cat_pg.php?P=S00_ChannelCNY- No Offense intended man, but the punch brace stock you are using is what 3/32 thick? I give the whole rig a 2-3 minute lifespan till it starts falling apart. What you need to find is the safety chain shielding like they use on highway mowers. Look at one at your nearest highway garage, and you'll see that the plate the chain hangs from is at least 1/4" thick and the chains are the same length, and there are no loops of chain, which could hook a septic cap, and Knock your whole contraption caterwhumpus, or worse yet flip it over or sideways. Please don't use this thing until you at least cut those loops of chain at the bottoms. You are in my prayers tonight.