Tom from SWISCO responded:
April 19, 2017
Thanks for posting, and for the clarification. That makes a lot more sense. Check out our S770-27 channel balance. I think this looks like a possible match. I think our 28C option should work for you. This carries a sash weight of 18 through 23 pounds. You may want to weigh your own sash to confirm. If you find it's less than 18 pounds, go with the 28B stamp option (12 through 18 pounds)
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