I still have some reservations about using the pliers this way to lower the backs of keys.
I will try to answer them
First of all I see a potential to disfigure the key cup since the pliers are pressing down on the cup itself and not the key arm.
By "disfigure" you mean distort the key cup or leaving marks on it?
Re distorting it, IME this is actually the method that is least likely to distort it. It puts the least pressure on different areas of the key cup itself. Other methods can distort it when using support under one area, for example if the key cup is relatively soft but the key arm is relatively hard (a pretty poor design).
Re leaving marks, the modified pliers are not only shaped in a certain way to fit different areas, but a lot of time is spent on shaping and polishing the surfaces that are going to touch the sax parts to prevent them leaving any marks. For example there are no rough surfaces there, sharp angles, very small contact points, etc. At worst case you can put some fabric between the key cup and pliers to be absolutely sure, but IME with them they don't leave marks if shaped exactly right.
Second, it seems to me that using the hinge tube as the fulcrum (like when bending the front of the key down) would work better than using the key arm as the fulcrum as is done in this case.
Depending on the shape and length of the key cup arm and the pliers, for some keys you can put the tip farther away under the hinge. In the photo it's almost under the hinge. In both cases the result is lowering the back of the key cup by bending the key cup arm. You could make a pair of pliers with two hooks at the end pointing up (when cut S is down) to use for levers on the key hinge. I would do that but I found it doesn't make a difference. So I prefer to have one pliers I can use for both since it's always necessary to bend back a little after any bend, so just more convenient (though sometimes it's unecessary to use the pliers to bend back).
In any event I will try this with my Ferree's key bending pliers to see for myself how well it works used in this manner.
I would be interested to know how it works, since yours are a significantly difference shape. Other than the "higher" bent tip (or "lower", depending on how you look at it) allowing to fit in more areas than the current stock pair, they still seems to prevent reaching some areas... or not? I'm also wondering how the surfaces are shaped for these uses. Anyway I would like to know how they work. I guess you might or might not be able to shape them to work better.
For lowering the backs of keys very slightly, there is always the old standby of putting a popsicle stick under the front of the key and giving the key arm at the back of the key a sharp rap with a plastic or rawhide mallet.
Yes, I do that sometimes, but a lot less since I started using these pliers. I always feel I prefer to use bending like this instead of tapping because it gives a lot more control for accuracy and there is less risk. Tapping is also "messy", having to hold the shim under the key while tapping all at the same time. For many keys you can barely reach so you need an "extension" e.g. a plastic or wood short rod to tap on, still all at the same time (possible but...).
At least that is IMO and IME