This is what I have for 100yds out to 250yds:
Largets is ~12H x 6W and smallest is 2H x 1.5W. It's good to have an assortment dependent on wind conditions. All my targets are A36 mild steel plasma cut 3/8" thick except the largest two which are only 1/4" thick. I got them off of eBay from Brian at Arkansas Custom Manf. Great guy to deal with. I had a local fabricator bend up some 3/8" round bar for stands and weld on the J-hooks.