A friend's house (about 50 years old) has what I believe are original
Pella windows that need a bit of sash work. The balance mechanisms are
aluminum or zinc and have a round hump profile - flat on both sides
and bulging out in the center. The sashes ride up and down on these
"humps" running in a channel or groove in both sides of the window. If
I remove the sash stops from the inside will the balances come out of
the jam with the sash?

Does anyone know where I can view a picture of exactly how the balance
connects to the sash, and what type of balance it is?

I need to remove 8 lower sashes to correct the hieght of the sash to
compensate for a botched job of cladding the outer framing and sill so
the windows can be latched. The cladding was done by a contractor
several years ago. They were looking at getting the windows replaced
and asked my opinion - I looked at them and the sash etc is all in
good shape, just cannot go down far enough for the sash latches to
engage so I need to either cut down the top or the bottom of the
window so the sash-latches will line up again (roughly 1/4")