Broken coil springs assemblies

I don't believe the Series 161 can work for you, no. Based on your dimensions and design I think you should instead consider our 15-228 pivot shoe. This is designed to work with either our 1/2" thick Series 160 or 3/8" thick Series 165. We also sell the 15-150S cover.

Review this hardware and the dimensions we show to confirm whether these will work for your window. 

Sure, that's almost certainly an 8. I think you'd be okay with using one 7.5 on each side, which adds up to 15 pounds of support altogether. Being only one pound off won't be the end of the world.

If you wanted to be more precise, you could use one 3.5 and one 4.5 spring on each side. That will total to 8 pounds per side for a total of 16 pounds of support, the only catch being that you're using an extra spring. If you wanted to go in that direction then you would need the 15-150D double spring cover instead of the single spring cover I recommended previously.

Either one should be fine, though. It's ultimately up to you.

You don't want your springs to be too strong. I know it seems like holding more weight is a better option, but that can actually be a bad thing. If your balance springs are too strong then your window will be more difficult to close and could actually open up on its own.

I don't think it'll be that bad if you order the 9 pound springs, but that's a 2 pound difference compared to your original configuration and that's starting to push it. You want to get as close to the original sash weight as possible. In my opinion, a 1 pound difference will be fine with minor noticeable effects. 2 pounds might be just a hair too far, even if you don't notice the differences at first. They'll become more apparent as the years go by.

Thank you, and you as well! If you had any other questions, please feel free to ask.