Hello, thanks for the reply. Here is my reply with pictures. However, I have taken a close look at the jamb liners, hooks, and balances. Here are my conclusions for these five double hung Marvin windows from circa 1988.
Jamb liners: Most of the jamb liners show wear (breakage, bending, cracking) at the top where the S hook attaches. The liners are 58 3/8 inch long x 3 3/4 inch wide not including the flexible vinyl on the outside.
Balances: These are 27 inch long x 9/16 inch wide. Inside the balance is a spring, cord, and a knife lock shoe. The shoe is colored blue. Appears to be a Ribbed Tilt Channel Balance. Could be exactly the same as your
Series 751 that is in one of your videos.
Hook: S hook is 2 1/8 inch long x 1/4 inch wide
Sashes: Are wood and aluminum clad. They are 1 3/8 inch thick and have a V plow.
Main cause of the problems appears to be the wear on the tops of the jamb liners where the S hook won't stay up and handle the tension from the sashes. Most of the wear is on the channel for the lower sash.
I am quite handy and I am considering reinforcing the backside of the top of the existing jambliner with a metal strap glued to the jambliner so it can handle the tension from the weight of the sash.
