Nice work so far wokka. For the swing arm, why not just cut off the stock side rails on the swing arm, re-weld in some longer ones ....reusing the stock top pivot tube and axle plates, welded back on. You could also weld in a cross brace , up near and behind the pivot tube to stiffen things up...... or for something stronger, an arch shaped gusset made out of 1/4" plate, welded in. The round Tubed swing may look better the Boxed? A 170 tire on the back? WOW ! Maybe a bit much for this little mill.