Window weight 11.6 lbs
Length of tube 31 inches
Width of tube 9/16
From my investigation the right part with bracket 17-012 # 32 should do the trick.
Let me know what you think.
Dan
Paul from SWISCO responded:
August 21, 2017
Hey, Dan! I agree, our Series 500 spiral balance and 17-012 is the first thing to come to mind. We've been using these to replace old wood window balances like yours for decades.