replacement quick-tilt springs

I thought I had ordered the correct replacement part (S140-4 : 4 lb Series 140 Quick-Tilt, Single) but clearly it is not the same. However, this new part seems to be much better constructed than the original part, which is made of extremely thin and flimsy plastic that has split apart.

What I am considering is installing the new left and right Quick-Tilt parts into the sash with a screw in the center to hold the top section in place. Do you think this will work? If not, do you have a replacement that will work that I can exchange it for?

The only identifying mark on the old part is patent #5,353,548. The metal spring has "8 GD" stamped on it.

Thank you!
Gary

What I thought was a meaningless blue "CC:" mark when viewed horizontally, I now realize is an "8". OK, so I must have a 8lb springs for the lower window.

So now I really do need to arrange for a return and a replacement, if you have something that will fit.

Thanks!