Trouble with replacing tilt window balancer

Hi,
The window like in pic 5 will barely hold a position when open, so I thought I should place the spiral balancers.
I ordered 4 series 400 35" spiral balancers last week and just installed two on a window.
Window now can half-hold like pic5.
I wonder that i may need to change the shoes too?
Pic 1 and 2 are shoes, if I need them, please help me identify them.

I also broke a "window foot" which attaches the window and insert the shows. I don't know how to call it.
Pic3 and pic4 shows what it is, please help me identify.
Thanks.
Gavin.

By the way, the pivot shoe is 3/8" thick.

Thanks for the reply, paul.
It looks like you are right that I compared with the old balance. S900-35 seems to be the answer.
But I have set that S400-35 successfully up by stucking it in the pivot shoe and it works partially.
What is the difference between s400 and s900? S900 can hold more weight?

Also, can you tell me which pivot shoe I should use if need some.

Thanks!

Thanks! I unstalled them.