Window Channel Balance Replacements

A home owner from Denver, CO says:
I am trying to determine which weight option to select, as I need to order several replacements. It seems that many of my window balances decided that this past year was the best time to break.

My current channel balances appear to match the 28" 350 Series (S350-28) and are stamped with a 2730; however my window sash weight is between 19-20lbs. Also, with working balances the windows do take some effort to lift, roughly 15lbs of force.

Following the weight guidelines provided, I am leaning towards the 2740 as the correct balance option, even though the balances being replaced are stamped 2730. Would there be a distinct disadvantage to either choice, 2730 vs 2740? Could you please provide your insight into this, as I seem to be borderline between the two options?
User submitted a photo of a window balance.
Profile picture of Tom
Tom from SWISCO responded:
Sure! In these situations, it's always better to go with the weight of the window sash. You never know if the original builders made a mistake or not. In this case, I think you'd be better off with the 2740, since two balances with this stamp can carry a window sash weight of 19 through 26 pounds.
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