pivot lock and springs

A quick learner from CT says:
I believe I found the right pivot lock shoes--swisco 15-175---.
The measurements are correct---1 1/4" wide--1 3/8" ht--9/16" depth.
However I am not sure which springs are the correct replacement---the sash weighs in at 13 1/2 to 14 lbs. Does that mean two 6 or 7 lb springs? s-1526 or s-1527 springs---one on each side? Enclosed are pictures----thank you for any help.
John T
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Tom from SWISCO responded:
Thanks for posting. What was the number on the old springs? If there is no number or if it's worn off, I think using our S152-7 spring would work. Each spring by itself can hold 7 pounds, so two working together can carry 14 pounds. Two S152-6 springs can only hold 12 pounds together, which is not near enough to carry your sash weight.
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