spiral sash balance question

A friend from Los Angeles California says:
I am considering spiral tube sash balances in lieu of counter weights in 1905 single hung (bottom)windows. I can't find weight and travel charts on line, so I'm asking for your help. The operable sash has a 3/8" x 3/8" groove for 9" from the top for the sash cord. Sashes weigh 8 1/2# to 8 3/4# each and travel 19 1/2". Which of your products would you recommend? I can be reached at 213 327 8055. Thank you very much.

Ben Davis

PS: you left 'Architect' off your list of categories, perhaps for good reason, so the best I could do was 'friend'.
User submitted a diagram of a window hardware.
Profile picture of Paul
Paul from SWISCO responded:
Thanks for posting! For a lower sash, I would go with our S400-20 red tip spiral balance. Two of these balances with a red tip will hold up to 20 pounds. I also recommend either the 17-030 or 17-031 bottom brackets. If you need a charging tool, use either our 75-004 or 75-005.
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