Can I replace these balances with your Series 770

A quick learner from Virginia says:
I have couple of question.

The current sash balancer is a simple spring with a shoe attached to it at the bottom. I have attached the pictures. I am thinking of replacing them with Series 770. Here are the questions:

1. If the length of the visible glass is 33.5", do I round it down or up? Do I select the 34" channel or the 33"?

2. I have attached the picture of the current shoe, the width of the channel is ~1". Which shoe do I need to select?

Thank you

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A quick learner from Virginia says:
Another question is can I use this balance with the wood windows?
Profile picture of Tom
Tom from SWISCO responded:

Thanks for reaching out to us. I'm afraid the Series 770 won't work for your window. In your case, the jamb liner itself is the balance. In my experience it's not possible to put another balance inside that liner. 

Is this a wood window? If so, you can contact a local mill work to set you up with new jamb liners. If not, you will need to contact the original manufacturer of the window for assistance.

We can at least replace the shoe itself, which would be our 20-022.

20-022 : Friction Shoe
Friction Shoe
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