Tom from SWISCO responded:
December 1, 2016
Start by looking at our S380-29 channel balance. This comes with the 19-005 top and 15-005 bottom. As long as these match, I think you'll be okay. As for the spring strength option, I think our 2820 is what you want. This often corresponds to the old 28B, but you can always weigh your sash to confirm.
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