Window won't close completely

A home owner from USA says:
August 25, 2017
My tilt windows won't close flat down when you shut them. You have to press down in between the locks in order the lock them and even at that both bottom corners of the sash pull up and the sash frame is actually bowed. The glass measures 31 1/4" . The metal tube measures 32" and is stamped with 32D. Could you help me find out why they do that and what part I might need to correct it ? Attached are the photos
User submitted photos of window hardware.
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Paul from SWISCO responded:
August 29, 2017
It sounds like your balance spring is too strong for your sash weight. Your current stamp, 32D, indicates a spring strength calibrated for sashes weighing 25 through 30 pounds. Can you confirm the exact weight of your sash? That would determine what you need.

As for the balance itself, it's very similar to our S770-32, however yours appears to have a hook like our 15-198 at the top. Can you show me how this is attached to the balance? Our S770-32 typically just screws into the frame, but I don't think that would be possible here. We may need to custom make it, I'm just not sure how that hook is attached.
A home owner from USA says:
August 31, 2017
The sash weight is 28 pounds.The hook at the top of the balance attaches through a whole in the window frame like is shown in the picture and the bottom of the hook appears to hook to a pin inside the balance.It looks a lot like your 19-029 to me.

This picture shows the pin which looks like your 19-029 would attach to the balance. The other end of the 19-029 goes in a whole in the window as you can see in one of the photos I sent in my first email. What would you think of trying a 32C in place of the 32D which seem to be to strong of a spring?
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Paul from SWISCO responded:
September 7, 2017
That is weird. If your sash is 28 pounds, then the 32D option should be perfect. If you are having trouble closing the sash, you may want to go with the 32C like you mentioned just to be safe. There may be some other hidden element affecting how the balance carries the sash.

Since your balance has a hook at the top, it iwll need to be custom made. Can you just tell me how many you need? Once we know that, I can email you a custom order link and price quote.
Pivot Shoe, 9/16" Thick
Pivot Shoe, 9/16" Thick
15-129
$2.50
32" Series 770 Balance
32" Series 770 Balance
S770-32
$13.67
Short S-Clip
Short S-Clip
19-029
$0.65
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